Keep track of how much you spend on a trip by hanging onto receipts for cash purchases and paying close attention to your credit card bills. When you get back home, sort through everything with your tripmates, figure out how much everyone is owed and settle up. Do this within your first week back from your trip. The longer you wait, the fuzzier the memories become and suddenly you’re fighting over money. No trip should have its memories ruined because you can’t recall who paid for you ugly friend to get his first handjob.