What I need to know when going to typical (traditional) wedding ceremony in Philippines?

I didn't want to just provide anecdotal notes, but since Mark Mayo encouraged it here are some -- I've been to several weddings in the Philippines and I've heard about many more.

The short answer to your question is: it varies. Wildly.

A lot of what the Wikipedia page says can happen, but none of it is guaranteed -- weddings are really up to the couple, their family and are often bound by how much money they have.

Weddings may be in a church, a resort, a hotel or on a beach, etc. Similarly the reception may be in the same place, or a different place an hours drive away.

There are some pointers I can give you -- for what it's worth Mark's advice is excellent.

Dress Code

Dress smart, you will be OK with a little less formal than you might do for a western wedding -- and remember it's hot and humid here so you'll be more comfortable. Philippine men wear a Barong Tagalog, you'll be fine not wearing one and shouldn't worry about it unless you really want to or you've been asked specifically to wear one. A white shirt, with smart trousers and nice shoes is fine -- I tend to wear a tie because I think it's appropriate but you'll get away without one in all but the most formal weddings. Jacket is optional -- chances are you'll be too hot with it on.

Ceremony

If it's a catholic ceremony it'll likely be like many others, with slight differences here or there. It'll likely be on the long side, and depending what they do there are parts where you're supposed to do or say something particular. You'll be able to pick it up easily enough and it's likely to be a lot less uptight and rigid than you might expect.

Traditions/Gifts

I'm assuming you're not part of the ceremony, bear in mind that there's an extended group of 'sponsors' who are involved. If you are one you'll be told what to do, but you'll probably be expected to give some money to the family (in a sealed envelope normally, someone will probably point out the right time).

Otherwise any normal gift is fine, including a card with cash which will be greatly appreciated and isn't frowned upon as it is in some places. Local currency please, whatever you're comfortable with, don't go overboard.

There may or may not be speeches. Don't expect anything like the traditional western format of father, best man, groom (is that the order?), more likely a few people will say some words. Speeches may or may not be in Tagalog, most likely they'll be in a hybrid of Tagalog and English (Taglish).

Reception

Receptions can be quite basic, there will be food, there may or may not be alcohol. Food might be catered, brought by guest pot-luck style or cooked by the family. It'll likely be buffet style. If you're lucky (and can eat pork) there'll be Lechon -- if it's a buffet head for that first, everyone else will.

Food is a good point -- if you have dietary restrictions you need to let the family know and possibly be prepared to eat in advance. Purely vegetarian dishes are rare (dishes may be only vegetable but there's likely meat in any stock). Similarly some common western allergies are just not common here and so aren't catered for.

Some receptions end after the food but you say it's a party -- so expect music and dancing. Expect a lot of cameras and picture taking. Possibly a roving video guy asking for soundbites from guests.

Just relax and enjoy. Nobody will judge you. People will make an effort to talk to you and find out more about you. Everyone will appreciate the effort you made to travel. I can't think of anything you could do that would offend anyone accidentally.

A few other things you may want to consider:

Timing -- depending how far you have to go make sure you have enough time. Traffic can be pretty bad and it can easily take you three times longer than it looks like it should. Arrive early, but expect things to run late. Make sure you know how you're getting between the two places if necessary.

Weather -- it's rainy season now, it almost certainly will rain at some point every day. And it'll rain a lot. If there's any chance you'll be caught outside have an umbrella with you.

Mosquitoes -- again if you'll be outside consider wearing and taking insect repellent. I wouldn't worry so much about disease but they're annoying as hell if they take a liking to you.