approaching someone randomly is really hard to do, and i think the perfect formula comes from who you're trying to pick up. basically. i think you should be extremely humble, polite, and confident, in the sense that you're talking to me confident, and not i'm gonna bang you and it'll be the best ever confident.  some chicks, do like a little push, but doing it in a silly way works better than being serious.  don't be a blow hard. be genuine.   i personally hate being approached by strangers. it's all too often some slobbering drunk, an old perv, or some douche bag. so make sure you qualify as none of the above.  most ladies you want to meet and date, will appreciate a gentlemen.
and i think girls often work the same as guys, one night stands, are one night stands. sometimes, they're more, platonic, or not, but usually, if you like a girl, save the sexy time for later.