Ensure you have a valid passport for all the countries you will visit or travel through; many countries require your passport to be valid for a longer period than the length of your stay (usually a minimum of 6 months), so check what applies to your itinerary. You might also need to obtain visas (depending on your nationality). Talk to your Embassy if you are unclear about what documentation you require.
It is a good idea to have copies of your passport details, insurance policy, visas and credit card numbers, keeping them separate from the originals and perhaps leaving an additional copy with someone at home.