Don't eat shrooms at school or before you have to do something like go to work, drive, or be around other people who you wouldn't want to be around while on drugs.
Take them with friends that are also going to be tripping and hopefully they've had experience with shrooms before.
Lots of people including myself enjoy listening to music while tripping and some people love to watch movies but I tried that once and while half baked was interesting it's more fun to go outside while tripping which we did later that night and some people love to trip in nature.
Eat 1-1.5g of dried shrooms or maybe 2.0g of dried shrooms if you've tripped before on excellent acid. Get a scale and measure them out, the whole 9 shrooms could be anything since mushrooms all weigh differently and they can be fresh or dried. Heh the 9 shrooms reminds me of how when I first heard about shrooms someone said to eat an 8th and I thought they meant take 8 mushrooms but that was when I was very young and before I learned the metric system.
Erowid.org has some excellent info on psychedelic mushrooms.
http://www.erowid.org/plants/mushrooms/mushrooms.shtml
www.shroomery.org has lots of info about mushrooms too and there's a trip calculator based on dosage and "levels" there but I don't think it's that effective as everyone reacts to drugs differently and I have had a very spiritual and intense trip with ego fragmentation while on just 2.0g of dried mushrooms.
Some people use benzos to cancel out a bad trip on shrooms or acid.
This is GHB or a depressant known as gamma-hydroxybutyrate.
http://www.erowid.org/chemicals/ghb/ghb.shtml
I've never taken it but when I was in HS this kid I knew had some but I didn't get any from him since I didn't know the purity, dose, or strength of the dose and you have to know that sort of stuff exactly. I know of a guy who drank way too much GHB and he died.
GHB isn't something you'd really want to take while tripping since shrooms can be sedating enough as it is with the heavy body load and I couldn't imagine why you'd want to take GHB or even drink lots of booze while tripping on them?