Use a floor jack and a block of wood...place the wood between the door and the jack as close as you can get to the hinge and VERY slowly start to crank the jack up. It will not pop right away...so pump it up just a little (you'll start to see it lift the body of the Jeep up off the suspension) and have someone put some weight on the Jeep to flex the suspension while you hang onto the door. Once it breaks free, it'll pop out of the hinges faster than just one person can catch it so always have someone there ready to catch it and keep it from smacking the ground or the side of your Jeep. Make sure you undo the strap inside so it doesn't hang up when it pops out.
Also, keep your windows rolled down...gives you better leverage and less chance of shattering the glass.
Before you reinstall the doors...clean the hinge pins real good with a scotch bright pad or fine grit sandpaper and then smear some all-purpose grease on the hinge pins. The doors will pop right off the next time. Remember to grease the pins occasionally to keep them nice and smooth.