I'm trying to omit opinion here to get some non-controversial things not to do with drugs (i.e., advice that'll definitely be useful for people who have decided to do drugs, regardless of their own opinions).
Advice That Isn't Opinion, You Just Don't Do These Things
Because there is nothing good about them (by any definition of 'good'), and something bad about them, the following "don't"s are a matter of fact:
- Don't smoke cocaine-salt: cocaine-hydrochloride burns (i.e., chemically decomposes) at roughly the temperature that it evaporates at. None of the chemicals it deteriorates into get you high; one of them is hydrochloric acid. So, don't smoke coke-salt.
- Don't do anything other than smoke freebase cocaine: it's weakly basic, meaning it won't dissolve in water. If you shove it up your nose, it'll just sit there being mildly corrosive.
- Don't overdose on water: having too much water flushes the electrolytes out of your blood, ironically causing symptoms identical to dehydration (including, e.g., passing out). In rare cases it can be fatal (see Leah Betts). If you're sweating a lot (e.g., raving on ecstasy) drink lots of orange juice, isotonic water, etc.
- Don't do too much whilst pregnant without checking first. Both alcohol and cocaine (and many others) can have severe retardation effects on developing fetuses.
- Don't inject into your artery. It's called intra-venous for a reason. It goes in your vein. Vein. If you've marred your veins so much that you need to inject into an artery, consider giving up instead. Arteries are smaller, and easier to block with substances that don't dissolve 100% in blood (e.g., heroin), leading to capillary blockage and thus gangrene. Ok, technically it's still your choice, and you might consider gangrene a fair trade-off (as it will still get you high), but still...
- Don't get caught.
Pretty Hard To Argue With Advice
The following have very little to commend them (no matter what your tastes) and a lot going against them; therefore, these "don't"s are opinion, but relatively universal. Unless you have a really weird attitude towards risk and/or what counts as 'fun' you should follow them.
- Don't make assumptions: drugs are dangerous and varied.
- Drug A != drug B: just because you've done alcohol, cannabis, cocaine and speed, doesn't mean LSD won't surprise you.
- A lot of drug A != a little of drug A: a large amount of mushrooms won't be the same as a small amount of mushrooms 'but more so'.
- Smoking drug A != injecting drug A: just because you know it's ok to do a drug one way, doesn't mean it's ok to do it another way, even if you know other drugs can be done that way. You shouldn't, e.g., inject alcohol, even tho you know it's safe to drink it and that other drugs can be injected. Confusingly, because both freebase and cocaine-hydrochloride are referred to as 'cocaine', just because you know it's ok to smoke cocaine (i.e., freebase), doesn't mean it's ok to smoke cocaine (i.e., salt).
- Drug A + drug B != drugs A and B: just because you've done drug A and enjoyed it, and done drug B and enjoyed it, doesn't mean you'd enjoy doing drugs A and B together. Some combinations, like cocaine and heroin, have greater health-risks than either drug on it's own. Some, like LSD and ecstasy, amplify the effects of one drug (x makes LSD trips more intense). Other combinations have results completely different to either drug on its own.
- Don't teach yourself to inject: if you're going to learn, only do so under supervision of someone who knows what they're doing. Don't just try to figure it out yourself; collapsed veins aren't nice. Doctors usually prefer not to inject, leaving it to anaesthetists or phlebotomists.
- Don't underestimate the following: cocaine, nicotine, heroin and (especially) methamphetamine are powerfully addictive and potentially fatal (or otherwize life-destroying), and should be treated with caution.
- Don't get addicted: addiction generally scores low on user-satisfaction surveys.
2009-12-7: Changed 'basic' to 'weakly basic', thanks to OldMiner for the correction; tidied punctuation.
2010-10-7: Spelling fixes, courtesy of Avalyn and my spell-checker