Drink low-strength alcohol
Eat before you drink - without food in your body alcohol absorbs quicker getting you drunk. if you eat food the alcohol doesn't absorb as quickly and you won't get as drunk.
Drink with a responsible group - Choose who you drink with who won't let you go home by yourself and won't take advantage of you if your drunk.
Personal - Age, Experience, Male or Female, Body Size, Mood, Personality
Drug - Type of Drug, how much taken, over what time, Strength of the drug
Environmental - Where used, with whom, on what occasion, Time of day/week, supervision