Crawl up in a ball and cry. I'd rather stay a girl, thanks. :D
I would just act the same. I wouldn't go and starting taking off my clothes to look/touch at certian places. I would find out what it is like to be a girl like see what differences they face in normal day life.
First i would start by fondling my newly aquired breasts. :]
That would probably last a few hours, then I'd eventually get bored of it, and just live my life normally ._.
Girls kick ass, but I would rather stay a guy, thanks. I just couldn't imagine having to pee sitting down o_O