I can not possibly endorse this or your wishes to go out as it is against the law, but..... there are some simple strategies for drinking at bars underage that i personally knuckled down and used without trouble right up until my 18th birthday (keep in mind I was a girl, so that undoubtedly helped):

Do not go drinking on your own, or with other underage friends. Go with older friends if possible (mid twenties). Sit somewhere out of the way, preferably out of the line of sight from the main bar where drinks will be purchased. Have your older friends buy your drinks from the bar for you. This is a normal thing that mates do for each other, but will also stop the potential for an ID confrontation once you are in . Go to small out of the way bars (do not even try to attempt going to any of the places that would be typically popular for people your age, like clubs or live music venues) If you want to go to a busier bar, go early. Like 3/4/5pm. Door staff often don't start until it gets dark. So if a bar usually has a bouncer, that may only come on after a certain time. Once your in, your in. Any interactions you do have with door staff or bar staff, be friendly and confident. Eye contact is fine, so is a smile. And if things are going south, don't wait to be told to leave, just get up and go yourself.

That, or wait a month, like a man.