Methamphetamine can be addictive, but only like 3% of people who use it become serious addicts. However, methamphetamine addiction can be very scary mainly because a meth addict can and will do literally anything to get more of the drug, and will neglect everything else. This has a lot to do with the fact that meth is expensive and not always easy to find though; if cigarettes were illegal, you would see smokers acting much the same way illegal drug addicts act.
Acetone is not bad for your teeth, it's not even toxic at all really. It's the hydrochloric acid you have to worry about. Also, if you use a lot of meth, that can dry out your mouth, which prevents your saliva from mineralizing your teeth. So if you eat and drink acidic stuff, this will wear your teeth away, and your saliva won't be there to do its job of maintaining them. In any case, when I was using meth, I was super meticulous about brushing my teeth twice a day because I didn't want anything to happen to my teeth. I think this is good advice for everyone who does end up using this stuff. Also, when I noticed myself start picking at my skin, I'd smoke a bowl of weed and go to sleep. Picking at your skin is a good sign that you need to stop, at least for me, and weed would always get rid of the meth effects, although YMMV.
Methamphetamine is not that flammable, but if the vapor is thick enough it can flash. If there are traces of solvent in the meth, that could increase its flammability too. Acetone evaporates so quickly that if you buy it, there wouldn't be any left by the time you got it home. And it has a strong, distinctive smell, like nail polish remover.
When I used it, I only used about a gram a month, which isn't really that much at all. I would get a pyrex test tube, then hold a torch on the side of the tube until it started to glow, then carefully blow into the tube so that a bubble would form on the red spot. Eventually, the bubble would burst, which would leave a hole in the side of the test tube. Then I'd drop some crystals in the tube and suck in to smoke it. It worked quite well all in all. You can get pyrex test tubes on ebay or whatever. They're maybe 50 cents each.
The ethanol/acetone mix (or methanol/acetone mix) is used to grow nice big shards. The way it works is, you dissolve the meth in ethanol or methanol, then add acetone. If crystals fall out, add more alcohol until it all dissolves. Then let it evaporate. It will leave behind big shards, and once it all evaporates, you can more easily dissolve away the impurities with acetone.
