International flight with layover - rechecking bags, customs?

Most airports of the world have one or more international transit areas which are completely separated from domestic flights, and in which passengers connecting via that airport from and to other countries do not need to pass immigration and formally enter that country. If your flights are on a single booking, then your checked baggage will be transferred for you and you will not go through an immigration check. In many airports you will still go through a security check between arrival and departure, or at the departure gate.

The exceptions to this are widely known: The USA requires all arriving passengers to formally enter the country and pass immigration and customs before connecting to their onward flight. Canada requires the same, except for onward flights departing to the USA on the same calendar day (and they are slowly moving toward full sterile transit as is done in the rest of the world). Dublin Airport is a lesser known exception with no sterile transit area, but in practice this only involves an immigration check and does not require re-checking baggage. The Schengen area is another well known area in which some 26 countries share a single external immigration border.

If you fly on separately booked tickets, this is called a self-connection, and in this case you almost always have to pass through immigration and customs and transfer your checked baggage yourself to your onward flight. The only exception I know of to this is at Dubai (DXB), where there is a paid service available at the airport which will transfer your baggage and check it in to your onward flight when you've booked separate tickets.

For your flights, you won't do anything in Amsterdam or Paris except go directly to your connecting flight by following the flight connections signage to your departure gate.

As you have booked connecting flights (they're on the same ticket/booking), given your itineraries, you will be checked through to your destination:

• At the point of departure, your bags will be tagged with the final destination. You will not see them again until you reach it.

• You will probably be issued boarding passes for both flights. In some cases, they may not be able to deliver the boarding pass for the second flight on departure, in which case you will need to visit a transfer desk at the connection airport. Transfer desks are "airside" (in the secure area), as opposed to the check-in desks which are "landside".

• Upon arrival at the connecting airport, you will probably need to go through security. Depending on your flights and which gate/terminal they use (especially in CDG), it may be just a bit of walking, or it may involve using internal-terminal buses or the inter-concourse people mover. You will not go through passport control in either case.

• In both directions, you'll go through immigration (passport control) at your final destination.

• In both cases, you will go through customs upon arrival at your final destination, after you have reclaimed your luggage. In Newcastle, since you will be arriving on what is still in practice an intra-EU flight (until the end of the year at least), you will be faced with 3 options: red, green and blue channels. The blue channel is reserved for people originating from the EU, and the tags on their luggage will have green stripes on the edges. You should use the red channel (if you have something to declare) or the green channel (if you don't).

Note for future readers: this answer is based on the specific circumstances of the question. Different transit points, different citizenships, different flights may work very differently in terms of through-check-in, baggage, passport control, customs, and visa requirements.