its been said but i'll say this again: what you're drinking, how fast you're drinking, and your own tolerance level are some of the main factors. also what you've had to eat and when.
if you throw up, big deal. yes, its not pleasant but its a lesson from your body. and it'll be that time then that you start to learn your own limits. at least thats my opinion on it all.
Pretty good summary, to my way of thinking. If you are mixing your drinks, (rather than sticking to one, i.e. beer, or wine), your chances of throwing up are greater. Likewise, if you are drinking on an empty stomach, ditto. It also depends on such subjective stuff as your basic mood. Drinking in a good mood, with easy going pals, is very different to drinking when you are really down; the latter tends to lead to gloomier depths, and possibly more throwing up.
My advice would be to drink plenty of water (nowadays - the voice of hard earned experience - I drink at least a large glass of water per round/pint/glass of wine; good for both stomach that night and head the next morning); eat before you hit the pubs; don't mix your drinks; and learn what you like to drink - some people can't handle spirits, others find wine gives them a vile hangover, etc, and learn what you are able to drink. Personally, I never drink anything already mixed; I prefer to do my own mixing when I drink spirits, that way, you can note what you are consuming. And I like robbieduncan's point (and agree with it); the gym analogy is splendidly, gloriously, ironically, apt; you do build up a tolerance if you drink regularly. And, yes, college days, wine and song and beer (and gutters, and falls, - my father - viewing me the following morning - referred to one spectacular night out on my part as resembling the Road to Calvary, the old "so Christ fell once, and twice, and three times", ah, yes); memories of bliss, and much else. Cheers