Peterpack as that was you're first post, welcome to this site. If you stay around here long enough and read the material, you'll probably develop into the state of mind where you do what you want, how you want, regardless of what others around you do, without worrying about what others will think.
With that said, lets go pack to your question. When you go to bars and clubs you should allow yourself to drink however much you desire, without worrying what your friends think, because this is your life and only you control what you do. If your friends are all getting hammered and you don't feel like you want to drink, you shouldn't drink. If your friends are sipping cola and remaining sobre, but you want to knock some beers back then go for it, because this is your life, and your night out.
If you're afraid of drinking too much and turning into the drunken fool and showing yourself up, then you need to change the way you are thinking, because when you're worrying about what people will think of you, you're limiting the amount of fun and enjoyment you can have, and you will feel awkard when you see everyone having the time of their life while you're there feeling all nervous.
Your question may look like it requires a simple answer, but theres more too it than just how much you drink. Some people have terrible game when their drunk, and turn into a needy chump, but for some people alcohol turns them into the ladysman many of us envy. You should go to bars in a sobre state and then in a drunken state and see in which state you have more fun in. Oh yeah, have fun