This information is general, for an specific country you should see the other posts.
Must of the countries ask for the birth certificate, passport, or ID. If you are divorced the certificate as well. (In a few countries also asked for the kids birth certificates of both parties, if you have any)
The Ceremony is usually in English in most countries but in some countries will be in Spanish and translate to English for a family member or a Coordinator.
Some countries ask for a health or medical certificate that needs to acquire 15 days prior to the date, and or required blood test, to be sure you don't have any medical problems. Others don't ask for any of them. Ask your Destination Wedding Professional before you travel for this information.
Usually, two witnesses are required, but some places, these witnesses can't be related to you