Treat women like people. Sometimes guy geeks have no problems talking to their buddies and then when a girl walks in the room, it's like silence...girls are people too. It's ok to talk around them, it's ok to talk to them.
Don't be a spaz when you talk to them. This is easier said that done, as spazziness has probably effected us all, especially if the other person is cute. Just try not to get to excited or jittery and that should help with the shakes. Probably some practice might be nice, so if see if you have any friends that know girls that you can practice with. Hopefully ones that you aren't interested in and are relatively normal.
To avoid the "Friend Zone" (see previous post regarding the dangers) don't treat them like one of the guys. Don't fart, burp, scratch your ass, or say really crude and sexist things around them. I'm not saying that girls are made of glass and need to be protected, I'm just saying that if you treat them like one of the guys, they aren't going to necessarily see you as future dating material.
Expanding on the friend zone idea, also don't be a jerk in general.

Don't be sleazy when you talking to women. Think of Howard from Big Bang Theory, normal women don't like him b/c he's slimey. We don't want slimey men. I
When you're talking to women, it's not dumbing it down, it's that you should talk about things they know. So if they know video games talk video games, if they're a Star Wars fan talk Boba Fett but if they start getting a glazed look in the eye from your treatise on how the replicants are a huge analogy for slavery (DUH!) then move on! But if she don't know about the topic but seems genuinely interested then go ahead and tell her about it, b/c maybe you'll convert her! :)
Here's an important point, just b/c you talk to a girl semi-regularly, or even regularly does not mean you are dating. It does not mean that she likes you in a potential boyfriend way. She might like you, but talking does not equal liking.
So here's to using more effective communication techniques in the future! Huzzah!
There isn't a great way to escape from it. Jumping from friend zone to boyfriend territory is a dangerous proposition b/c oftentimes the girl will get freaked out and will just start avoiding you in general. It's just really awkward.
Now if she hasn't been pulling a
So what to do about this? Make sure that you don't do everything together. As much as you guys like each other, you're also two individuals. Especially if you work and live together, make sure that you still find time apart just so you remember what it's like to be on your own. Establish some things that you can do apart and both have fun. Say if one of you watched football, then the other person can establish a video game day on Sundays. Don't necessarily do chores b/c if one of you is having fun and other is working, I think that can lead to a lot of resentment. And resentment leads to arguing and arguing leads to anger. Anger leads to hate. Hate leads to suffering. (Yoda is so wise his sayings have a much broader application than just jedis!)