Confidence comes from practice, I'm afraid. And, occasionally, alcohol....but practice generally yields better results.

Definately go over, ANY excuse will do. Have a reason, or just walk right to her. Frankly, seeing someone making a beeline for me across the room CAN be sexy as hell. That he's gotten up the nerve to introduce himself to me is a compliment.

When is more of an artform. There are points in every mixer type party when I'm so bored I want to start peeling the paint off the walls. If you're nervous, that's a really GOOD time to talk to me (and I'm guessing most other people), because I will be more than willing to help jump start a conversation.

As far as conversational topics, sometimes it's best to choose an opener that requires her participation. "That's an interesting lampshade the host is wearing," doesn't necessarily require as much from her as, "What do you think of our host's new headgear." If you follow me. Also, introduce yourself if you don't already know her. It doesn't have to be the first thing you say, although it can be. It's polite, and helps make a connection. It's a great way to show a non-threatening interest.

To add to the list of don'ts....don't use the pick-up line a drunken friend of mine claims to have tried. "Hi, I really hate your jacket. It's cute, and all, but I can't see your ass when you're wearing it." It didn't work, but I'm happy to report she didn't actually break his nose either .