I've done the spark plug thing on my first car, a 68 Cougar.
Another one I learned on this car is to chock the wheels when it is on the ramps.
The shifter was real sloppy, the guy i bought it off of told me it needed some new bushings. The shifter was so bad I could pull it out of park without pushing the button. (C-4 with a floor shifter...all stock) Just pull that laver off the the side while pulling it back and it would pop out of park.
So here I am, a scrawney 100 pound kid, under this car up on the yard sale ramps I bought that morning. I am laying on my skate board since I didn't have a creeper and refused to get my brand new jeans and Metalica T-shirt (also bought that morning) dirty. I see an arm sticking down to the tranny, and reached up to grab it saying to myself "this must be the shifter." All of a sudden, it moved as I wiggled it back and forth....but it moved forward...as the car started to move backwards.
I was able to get off the skate board, and I grabbed the bellhousing of the tranny trying to slow this huge car down as it started to actually roll down the ramps. (remember i was a scrawney 100 pound 16 year old.)
I was looking right at this big bolt on the bottom of the engine (oil pan drain plug) coming down twards my face as the car refused to stop. I couldn't understand why I couldn't stop it. I turned my head on its side as the drain plug came down on me, cutting my cheek a little.
The car was really starting to move now. (at least from where I was looking it was hauling ass anyways) Now it is off the ramps, rolling in the fairly level driveway, but it is only 5 or so feet from the street...all i could think about was my new T-shirt and Jeans.
As the rear tires were going up the crest of the street, and the rear tires had not hit the gutter yet. i quickly rolled out and was nearly hit by the front tire. I jumped up cussing up a storm grease all over my face and hands, shirt shreaded in the backs from the not so smooth driveway, and I had not realized it yet, but I was bleeding too. Both on my face, and my back was all scratched up too.
The only thing that made this wores, was the POS wouldn't start (Hmmm, might have been the loose spark plugs and the junk holley carb that leaked more gas than it fed the engine) So there I am, my butt 1/2 exposed, my back and face bleeding, and I am trying to push this tank into the driveway.
This was also the day i realized my parking brake wasn't worth squat.
I was OK though, just minor cuts and a seriouse damaged ego...I was seen by some friends pushing the car and bleeding all over the trunk lid as I was pushing.
They had diareah of the mouth and the whole friggen school knew before the next day.