Let me say a word about jack stands. The car is going to be up in the air with you under it. If it falls on you, you will probably die. Please use good quality stands with a lot of excess weight bearing capacity. Some stands are not much more than a steel tube that had been split three ways with a little reinforcing. Please do not use this kind. Good jack stands usually have four stout legs and an adjustable height cast iron seat. Even then be carefull.
Crazy as it sounds, after putting the car up on stands, I like to stand by the car and shake, push, pull, whatever on the body as hard as I can. If it is going to drop, better when I am next to it and only the car and floor suffers.
For extra protection, I usually slide the tire I have removed under the cars' frame rail. Why am I so careful? I had a car fall off a scissors jack once when I was young and foolish. I was lucky enough to be just forward of the front bumper when it happened. Dense as I was, I got the message. Now I have 3ton and 6 ton jackstands and a good 3.5 ton flat jack.
Funny thing: I was once taking loose the differential drain plug on my old 560SEL (126 body). I had a breaker bar and pipe extension like was mentioned (great idea, btw). I was putting so much torque on the plug (180 pound me on a 4 foot bar =?), I started to worry that I would twist the car right off the jackstands. Plug did come loose first.
Oh, and a 24oz. ball-peen hammer can be real useful too.