Soak the bolts with penetrating oil to help loosen up any rust and built up gunk! Put a bunch on and repeat a few times until your next battle with the wrench. Also tap the bolt head with a hammer. This will help loosen things up also. If all else fails a little heat from a tourch may help (just be aware of your surroundings...wiring, fuel lines, etc.).
Also, I have no idea what kind of tools your using but, in the long run one good tool is cheaper than 2+ cheap tools.