Q. What if the ground is soft? A. I have had jacks sink into the dirt and not lift the car at all. To fix that I looked for debris on the side of the road. I was lucky and found some plywood to put under the jack.
Q. What if I can't get to level ground? A. Look for some good sized stones or bricks (something that wont move) and cram it under the other 3 tires. Allow the car to roll back on them a bit before you engage the E brake and jack the car.
Q. What if I cant loosen the nut? A. Try hitting the nut a few times, it may help to loosen the crud and crust. Didn't help? Try standing on the tire iron and use your body weight to loosen it. Or you can use the jack to lift the wrench. Or if you have a pipe near, you can slip it over the tire iron and use it for extra leverage.
Q. I am an idiot and lost all 5 nuts and now can't secure the tire, what do I do? A. Take one nut off each off the other 3 tires and drive home like an old lady on Sunday.