I'm a little late to the party but I'd like to chime in.
A good deal of alcohol tolerance just depends on your experience. If you're the type of person that needs to ask this question to be sure, then chances are the answer to your question is "not too many shots." That's nothing to be ashamed of; any accomplished drinker was green to this at one point.
Truthfully speaking, you probably should stick to beer or (preferably) wine* at this point. However, if you're a rookie and you insist on drinking spirits, then I'd recommend that you drink it over ice cubes. Chances are, your palate isn't too accustomed to the taste of straight alcohol, and that'll help you pace yourself. Mixers can be deceptive and you won't realize how deep of a hole you're digging.
Perhaps the most insidious aspect of drinking is when people (usually men) try to measure how much they're able to drink as a dick-measuring contest, or a point of pride. That mentality literally kills people, and I'm not piping up as some lightweight - I've been on a thirty-six hour bender before. Please don't fall into that trap.
Happy drinking
. Shoot me a PM if you want more tips.
*This deserves emphasis. In my younger days, a .750 of White Zin from a gas station was a great way to start the night and feel bubbly.
