1) push the tyre into the middle of the rim - if it's a deeper channel there the bead will be easier to set
2) Do not use sharp tools to put the bead on, in the last 3 years (and about 1000+ tyre changes) i've only seen one rim/tyre combo that was too tight for the standard lever
3) Take small bites out of the last bit of bead. Do not try to put the entire last section on all at once - you'll break the levers as you've found out. With experience you'll know how much is too much just by the force on the lever.

And for other lame things like - make sure you're putting on the correct tyre for the correct sized rim. For example you can with great difficulty force a 700c tyre onto a 27" rim.