There's a brief piece on Jezebel about modern chivalry, (and some of it is pretty dirty, so beware), but there's one bit that I think every guy should know and practice: The bit about getting into a cab first.
Seriously, I know it SEEMS like the chivalrous act is to hold the door open, but it's not. Especially when the lady you're with is wearing a dress or a skirt. That just means she has to crawl in, try not to flash you as she does so, and then slide over and probably get her dress all scrunched and wrinkled in the process. And then she'll have to do the same thing when it's time to get out. Not fun.
So dudes. Get into the cab first. Always.