1. Put your chain onto the big chainring. That's very very important. If you've already taken the chain off of the bike, put your first aid kit somewhere where it'll be handy when you bang your hand on the chainring.
2. The crankarm bolts turn counterclockwise to loosen on both sides so be sure you are trying to them the correct way.
3. Do whatever you have to do to get it to turn. I've found it helpful to align my wrench with the crankarm so that I can squeeze the two together.