Hmm...this seems to be a matter of luck rather than a matter of style. What kind of wardrobe is this friend of yours wearing now? As a girl, I'd have to say I'm attracted to dressy button-up shirts with collars and nice pants(PLEASE TO GAWD NO COWBOY PANTS...my eyes, they burneth with PAIN!x.x). Ties are sexy, too. Especially geeky ties, like ones with binary on them, or like my Art History teacher who wears a different tie every day, ranging from the Three Stooges to Spiderman. He's awesome.XD Remember, keep a little hint of his interests in his wardrobe; that way, he'll attract girls that are to his liking as well as her's. That's why I recommend the tie thing.

Now, as for avoiding flaky girls...hm. This is a tougher question. Usually, it's the hyper ones you need to watch out for; if they're overly energetic, I've noticed they're a little on the flaky side. Now, it's okay if they're hyper once in a while, but make sure they're somewhat steady in the head. Keep an eye out for the shy ones, or the ones with the mopey faces in the corner at nightclubs who don't look like they want to be there at all. You know, the one who's dragged in there by her friends, despite hating places like nightclubs with a passion? That's the girl your friend could try going for. Be wary, however; stick with your friend when you approach these girls. They might get hit on a lot. As a warning, do NOT use a cheesy pick-up line.

Yes, I'm totally making a lot of this up, but bear with me. It seems plausible enough in my mind, considering I've got a lot of friends who I enjoy being around that are always dragged into places like this one nightclub nearby, and they tend to mope around the bar area.