Women don't mind a shy guy, as long as he doesn't act creepy. There's a crucial difference between shy and creepy! Unfortunately, part of it is looks: if you look rundown, unkempt, overly nervous, these things could work against you. In that case, my advice is to dress well, cleanly, but with your style, and go to your barber regularly (shave/clean haircut). If you have a beard, keep it neat. And Always remember good hygiene! Deoderant my friend.
That said, I do think when you dress well, you feel good! However, you may still feel shy, or somehow unworthy. It definitely helps to be around friends who can boost your confidence, but if you don't have that, do it for yourself. I don't know what guys do, but I like to do things I'm good at. So if I'm going out, I sing while getting ready... it brings my mood up, and gives me a confidence boost.
When you talk to women, try to be yourself. It sounds cliche, but believe me, if you put on some kind of tough guy personality that isn't yours, if you try too hard to impress, Women Will Notice! Just be nice, start off with a compliment (never backhanded: we don't like to be told you're amazed that we are pretty AND smart...) and go from there. If you can relax a little, the conversation will flow. It helps if you ask questions about her, and then listen. Ask what she likes to do, what her job is, travel, etc...and maybe you have something in common.
Last, and least, if you are out or at a bar, having a drink doesn't hurt. Don't drink too much! But if you can drink, I know that it helps me get over my inner critic, and feel more relaxed. If you need this just to get the first conversation going, its fine! No one should rely on substances to socialize, but if you're very nervous, for a first meeting one or two drinks can't hurt. Don't get drunk! And don't act like you want to get her drunk! Also, if you buy her a drink, make sure it's what she likes: Ask if you may buy her one, and then ask what she likes. Common sense, but sometimes guys miss this one.
**You're Acting Creepy When:
-She's 10-15+ years younger
-She acts bored, nervous, or repeatedly looks around as if for friends
-She frowns, tells you in some obvious way that she doesn't like what you're doing
-She's dancing on the floor and you come up behind her and start grinding, no permission! Gross! **