Actually find out what having one standard drink (just one beer/hard lemonade/wine/whatever) will do to me. I'm guessing that it'll hit me really really hard even in a small amount (I'm female, small, and have no tolerance for alcohol whatsoever), but I think it would be useful to know.
And seriously, if I don't make this a resolution, I probably won't do it, lol. I have to resolve to drink.