There was this one recent post where a Dood clasped his crankarm to his Park workstand and used that to get better leverage to free his pedals. That would work as well as putting it in a Vise Grip or getting someone else to hold the other crankarm in place while you torque that Pedal wrench down with all your might.

There is a technique for getting the best leverage if you are doing it yourself. Position yourself so you can hold the opposite crankarm in place(usually you have to swing your arms over the top tube of the frame) while you try to free the pedal lose. Use parts of your body for more leverage. I like to use my Thunder thighs for this. This technique is all about using opposing forces. Push the opposite crankarm in the direction necessary for the best leverage.

Also, try to get a long ass metal pipe and put it over the end of your wrench for more leverage.

One technique that I've used in the pass, but don't really use anymore is to get a hammer and bang on the wrench. All you need is one good shot and you'll have free pedals. You really need someone else for this. One to hold the wrench in place while making sure the crankarms don't move and the other to use the hammer. The key is to reduce any play on the wrench to maximize the force towards whatever direction you are hitting. I'll say a bolted down Vise Grip and a Hammer should work nicely. The longer the wrench and the thicker the wrench interface, the better.

Or just go to your local gym and find a meathead weigthlifter and ask him for help. Those muscles should be used for something other than good looks. You can buy him a protein shake infused with 'roids.

Problem Solved.