I couldn't get into a nightclub until I was legal age (18). It was because at the clubs, they have people checking for ID's at the door, so without one, you weren't getting in.

Pubs are easier to get into though. They don't check for ID at the door, and if you look of age, there's a good chance they'll serve you.

I used have a buddy when I was 18 who was only 17, so what he did is he went off the washroom while I ordered a jug of beer and 2 glasses. They'd bring the beer over, he'd come back, and viola! He'd start drinking.