Know your limits. Whatever ever you're doing in life, that's pretty solid advice.
When it comes to drinking alcohol, I usually know mine . . . depending on whatever it is that I am imbibing. For example, I know how many beers I can drink before I've had to many . . . it's the safest thing for me to drink. Wine . . . I love it and therein lies the problem . . . I can drink a whole bottle by myself before i know what's happened and by then I'm stupid drunk and a big sloppy mess. Hard liquor . . . I adore martini's, not your floofy girly concoctions that are popping up everywhere, but a classic gin martini with half a drop of dry vermouth and olives; one and I'm pleasantly buzzed, two and I'm drunk, three and I'm a big mess. That being said, just because I know my limitations doesn't mean that I observe them . . . stuff happens.
How much you can drink before it affects you depends on a lot of factors. How much you should drink is something else entirely. It depends on where you are and what you’re doing, whether you’re staying or going, empty stomach or not, you physical make up, etc.
Keep in mind that 1.5 ounces of liquor has roughly the same amount of alcohol as 12 ounces of beer. Shots may be small but they still contain a lot of alcohol. It doesn't take much booze to make you legally drunk, and alcohol stays in your system for hours before it is all gone . . . figure two drinks in an hour for someone who weighs 150 pounds. That being said, it usually takes more then 2 drinks to get drunk. It will most likely take 7 or 8 beers to get you drunk if your 150lbs.
Personally, I don’t care if you get drunk, act stupid and embarrass yourself in front of a roomful of people . . . so long as you’re staying put. I do care if you get drunk and do something that will affect me or someone else . . . like driving.
So, again, know you’re limitations. Be safe and don’t be stupid.