What are the characteristics of karmaless action?

No one can avoid any kamma in a very long travel in saṅsāravaṭṭa, except niyata-bodhisatta (bodhisatta who has enough experience to be an inevitable person to enlighten as buddha).

However, niyata-bodhisatta still born in hell, except just avīci-hell, still born as animals, except just very small and very big body animals, etc.

So, although you are bodhisatta, you still can not avoid the hell.

In commentary's statistic, just attained jhāna people have an enough long lifetime to get a very small chance to meet metteyya-buddha in present life, and just angels in 4th jhāna sphere and anāgāmi-ariya in no 5 string sphere have a lifetime that long enough to get a very small chance to meet next buddha after metteyya-buddha.

The other people, such as all 1st-6th heaven people and all human, will die before the next meeting buddha, and their death can lead them to the hell uncountable time, before their next meeting buddha.

Bodhisatta develop their wholesome minds without any fear, although they realizing that they will born in hell uncountable time before the enlightenment.

So, if you don't expect to be a new buddha, just this life is the easiest way to enlighten for you.

This is an important question for the person practicing Theravadin mindfulness meditation because its answer is relevant to understanding how this meditation works. But first some background information. In Theravadin Buddhist psychology, “karma” includes both bodily and mental action. For example, decision-making is a form of mental action. And, although the Theravadin Abhidhamma does not talk about unconscious cognitive processes, karma includes unconscious decision-making. There are four types of action (karma in Sanskrit, kamma in Pali): (1) Wholesome action (kusala), (2) unwholesome (akusala), (3) karma-resultant (vipaka), and (4) not wholesome, not unwholesome, and not karma-resultant (aryakata, kiriya, or kiriya-citta, sometimes called functional consciousness). Your question is about the fourth type. I will call it functional mental action. Finally, all actions are caused by sankhara, which is best understood as schemata (in the sense defined by Immanuel Kant). Sankhara are the products of mental evolution or learning. The sankhara that cause functional mental actions are all products of an ancient evolution of consciousness.

The kiriya-sankhara have the function of causing a person to act as intelligently as possible, even when he or she is in an unwholesome state of mind. In terms of modern psychology, the kiriya-sankhara generate “core knowledge,” knowledge discovered to be present in young infants by Elizabeth Spelke. Of course, the kiriya-sankhara continue to generate core knowledge throughout our lives. In Mahayana Buddhism, the kiriya-sankhara cause the complex and important cognitive processes referred to as the Bodhicitta.

The kiriya-sankhara cause several types of functional mental actions. By far the most important functional mental action (in this case, an unconscious cognitive process) is one that causes us to make sense of potential actions and make sense of what we experience. This is an automatic and largely unconscious process that we take totally for granted, yet is essential to understanding Buddhist psychology and the kiriya-sankhara.

This most basic nature of all sankhara gives us a fundamental insight in the minds of the Buddha, greatest teachers of Buddha-Dharma, and the ordinary person alike. The reality is that we all, without exception, make sense of things (everything!) by means of the sankhara we possess. Only by means of a sankhara (or schema) does a sensation become a perception. Only by means of a sankhara does a feeling make sense to us. We cannot perform any action unless it makes sense to us by means of a sankhara. It is only by means of sankhara that we understand other people or ourselves. A sankhara (or schema) is a set of predispositions (beliefs, values, attitudes, memories, understandings, or the like) that allow us to process (mostly by means of unconscious mental processes) meaningless data into meaningful information (action, knowledge, belief, even illusion). Only through our sankhara are we able to be intelligent in the most basic or brilliant way. And one more important fact: all sankhara are finite in scope and understanding. There is no such thing as an infinite sankhara or an infinite understanding. It is psychologically not possible to know everything about something. Wisdom must necessarily mean knowing what is most important or relevant about something. This is an inherent limitation of the human mind, even the mind of a Buddha or a genius. (Buddhists do not talk about gods.)

What does this mean for the beginner of mindfulness meditation practice? It means that overcoming suffering, making progress on the Path, and undergoing Enlightenment itself consists entirely of unlearning unwise sankhara and learning wiser sankhara. The hard part is working out the details! It is your kiriya-sankhara that make both learning and unlearning possible.

...what are the characteristics of karmaless actions?

There's only one characteristic - for truth, it's Selfless/Anatman (無我) action. All Karmas are doing (actions), all doings signify there the doers. When the doer has ceased, there's no doing, hence no Karma.

It's not my invention :). It's what Nagarjuna said. Read his Madhyamaka in Chinese original if you could, not the Tibetan or Sanskrit translated English ones though. Almost all of those Eng. versions you could find are from Tib. or San. these scholars being taken thinking those more exotic or authentic; yet the truth is, they were back-translated from Chinese, of inaccuracy. The whole Sastra included "Blue Eyes" explanation by Kumarajiva is only 68 pages, full of witty remarks.

The other way to help pondering Karmaless action is the Daoist: 無為 而無不為 -- Dao De Jing.

More it's close to a Selfless action, lesser the Karmic implication. Until one realized Anatman, then all his doings are Karmaless doings. Too many people believing once they know the concept, learn the theory or argument, or read the Suttas of Anatta, etc., they have the privileges of having the Anatta. It's so unhealthy even fatal for their Dharma lives. It must be stressed, the proof of really realizing Anatman is one can disappear at will. Again, it's not my invention, it's described in the Sutras and Vinayas I read, such as, a Bhiksu disappeared right in front of the eyes of the visitors from the rock he sat to report to the Buddha then reappeared right at the same spot telling the Buddha was on his way from Grdhrakūta.

DukeZhou, who ever finds intereset,

reading the question, the answers and comments a little, looking for possible places to make a benefical share, possible correcting, possible filling lacks, possible provoking skillful thoughts, possible to proper perception of the path to release, and therefore possible leading to abonding, disenchantment, release:

A person unknowing: the actions performed by him, born of greed, born of aversion, & born of delusion, whether many or few, are experienced right here: no other ground is found.

So a monk, knowing, (eg. Arahat) sheds greed, aversion, & delusion; giving rise to clear knowledge, he sheds all bad destinations.

AN 3.33

When the root of kamma, not-knowing (avijjā), is up-rooted, abonded, reminderless destoyed, with the lack of effluents of the mind (which is also the root for lobha and dosa), no more kamma comes into be.

Note, since it is often misunderstood missinterprated. Such as "neutral (avyākata) kamma" is not all a kamma with no results.

Kamma of a mind that is not released from not-knowing, even if neither skillful nor unskillful, does neither cause increase nor decrease not-knowing. Therefore, dwelling in a neutal mind-state (which has not abounded not-knowing) still has the quality of wandering on in the kammic circle, has it's effects.

Dwelling in "non-action" which actually is not, therefore makes no sense for release. Skillful actions are required as base to uproot avijjā, to develop the path.

So called Zazen or only samatta are no means for liberation in and off themselves.

Even a "neutral" mind state (yet mind still deluded), dwelling on such stand, is conditioned, subject to becoming and all of which is originated is subject to decay.

One seeks for kammic consequences which are cutting off, needs to cause a result of cutting off, come to a state beyound states, unbinding, release.

*‘‘Katamañca, bhikkhave, kammaṃ akaṇhaasukkaṃ akaṇhaasukkavipākaṃ kammakkhayāya saṃvattati? Sammādiṭṭhi…pe… sammāsamādhi. Idaṃ vuccati, bhikkhave, kammaṃ akaṇhaasukkaṃ akaṇhaasukkavipākaṃ kammakkhayāya saṃvattati. Imāni kho, bhikkhave, cattāri kammāni mayā sayaṃ abhiññā sacchikatvā paveditānī’’ti. *

"And what is kamma that is neither dark nor bright with neither dark nor bright result, leading to the ending of kamma? Right view, right resolve, right speech, right action, right livelihood, right effort, right mindfulness, right concentration. This is called kamma that is neither dark nor bright with neither dark nor bright result, leading to the ending of kamma.

Ariyamagga Sutta: The Noble Path

Therefore:

Assuming one has to operate in the temporal sphere, but seeks to diminish the karmic implications of action, what are the characteristics of karmaless actions?

One who operates, if there is a notion of one who operates, causes kamma and results. The results of "neutral" kamma, depending on the quality of mind, leads to either pleasant, unpleasant or functional results.

The chatacteristic of kamma-less actions is, that such are based on realeased mind.

Is this distinct from right action?

This is distinct of right action yes. Right kamma, neutral kamma, kamma that leads to an end of kamma and such deeds without results, are differnt Dhammas.

For more on ending kamma (if that's the questions underlying purpose at least, or answer had lead to this, if not solved yet) one may see further: MN 57; "Kamma and the Ending of Kamma" in The Wings to Awakening

Consider also, if thinking to "boddhisatta"-around the compassioned advice of Upasaka Warapol, on the possible root-inclination of the question, here. Hopeless overestimating, while mostly not capable to keep basic precepts, even fear of having no electricity but thinking a strive for a more noble then a noble, is very common, here, and today like all the time.

[Note: This is a gift of Dhamma, not meant for commercial purpose and other low wordily gains by means of trade and exchange]

What are the characteristics of karmaless action?

It leads to dispassion.

Meaning, it's an action that reduces both karmic as well as mental / emotional entanglement.

Normal pathological action leads to entanglement in issues and trouble. Typical example is a child of a dysfunctional family, who is forced to inherit the bad circumstances and negative inertia, and by reacting destructively keeps creating causes for future trouble. Normal success-oriented action leads to positive entanglement in worldly affairs. Such as, when you are realizing yourself as a successful professional in any field.

Supramundane action leads to dispassion, to disentanglement, to letting go, to unbinding. How? Through counteracting/taming the forces of desire, aversion, and confusion.

So every time you act (whether directly or indirectly) towards reduction of desire, reduction of aversion, increase of wisdom - that's the supramundane action.

You can act towards reduction of desire and aversion by directly suppressing them and letting go - and realize wisdom as you practice this ("samatha followed by vipassana" in the broad sense). Or you can pursue wisdom and realize reduction of desire and aversion, and eventual dispassion - as a product of wisdom ("vipassana followed by samatha" metaphorically speaking). This is a theoretical construct meant to made the point. In practice everyone has to do both, in a spiral fashion - emotional intelligence and wisdom developing in lockstep.

While "karmaless" action can be ensured in the most straightforward way by literally leaving the world and engaging in practice of meditation (an approach typical of Theravada), a more effective approach, IMHO, is the Mahayana practice of not letting your ego indulge in self-sustaining activities. In other words, you should only do what leads to objectively optimal result (within the limits of your practical ability to achieve the optimum in the midst of a real life situation) and never let your social image, your ego, your group/tribe ego, your fears, your pride, (including your spiritual pride!), your bias etc. to get a bite of nutrition. This way all of your action will go towards dispassion and wisdom, as it will not be motivated by an egoistic motive (aka "passion").

Now, for the wisdom leg, this wisdom is not the worldly wisdom either. It is the special wisdom of understanding the nature of phenomena and mind, the nature of reality so to speak. So any action toward pursuit of this wisdom counts as "karmaless" action (action that leads to the ending of karma).

One notable characteristic of special wisdom is abandonment of overgeneralization and stereotyping. This leads to action that itself is not based on overgeneralization, stereotyping, and passionate side-taking - and encourages others to avoid overgeneralization, stereotyping, and passionate side-taking. Enlightened/enlightening action is inherently peaceful and brings peace.