What should I wear/do with my make up to make me look my age?

I've always looked young for my age. There are countless examples of me buying an M-rated video game or R-rated movie and the clerk being skeptical of my ID. One guy even told me that I should never go to a club because they would confie my license, believing it to be a fake. The problem is, one of my friends wants to go to a club for 18-21 year-olds on his upcoming nineteenth birthday. I will myself be 19 by the time it rolls around. But I'm especially anxious because today the campus security guard at my college almost kicked me off campus because she thought I was too young to be a student there. She asked for my student id, and when I couldn't provide it, I showed her my textbooks. She still didn't believe me. Luckily one of my friends came to my aid. I'm tired of this happening and I don't want the bouncer guy at the club taking away my ID. Any make up or clothing tutorials would be much appreciated. =\