Look for current currency first--some like Australian $1, $2 coin and stuff are worth current value and it may be worth hanging onto if you have enough of them to say, trade to someone going to that country. Then, look for old stuff, pre-WWII, for instance, clearly anything that might be silver, or have gold content, etc. It may be a painstaking task to try and winnow it down to anything worthwhile, but I guess it depends how much time you have and how poor you are. You're going to have tons of worthless ones, worth less than ten cents each no matter what way you sell them. Those are the ones you need to bundle up and put on E-bay, making sure your shipping cost covers the packaging and all. Or you might sell them at a local craft show, collectible show, gunshow, or whatever, if you have enough of them to bother with a table, or subrenting from somebody else's table and/or have them sell them for you. Packs of random foreign coins for say, $3 apiece or whatever. Or give them to your kids to take to school and sell....etc. etc. etc.
