Having worked in a garage for quite a while, the trick is leverage. If you have a little 6 inch long ratchet don't expect to have an easy time getting these suckers off... get the longest wrench that will fix and apply pressure to the very end of the handle... if you have a short pipe you can also put the end of the wrench into the pipe to gain some extra leverage.
Make sure you have the car securely lifted on jack stands before trying to get it off... the last thing you want is for the car to come down on top of you while you're working at these bolts. If that car comes down you WILL BE SERIOUSLY INJURED AND/OR DIE.
You can also try to use your legs... lie on the drivers side of the car with your legs pointing towards the passengers side and put one foot one wrench. DO NOT KICK IT. That's a good way to BE SERIOUSLY INJURED AND/OR DIE. Instead of kicking, apply gradual pressure to the wrench... your foot should never not be touching the wrench (that would be a kick). If you can "rock" the pressure (imagine a kick, but without your foot ever coming off the wrench) you should be able to get it off in 3-4 "rocks".