One more safety tip:
NEVER put your hand on the top of a high lift jack while it has a load on it! I saw a guy get caught when the car rolled forward and pinched his hand between the jack and the car. Somehow, three of us kids were able to roll it back and let him get free. It would have been a long day for him if we hadn't been there. Of course, wheel chocks would have kept it all from happening, but. . .