In the past week I got a #/k-close and then a separate f-close. I've seen an improvement in my comfort level around attractive girls. Here are some things that could explain why:

First of all, I saw another post on the front page today by a guy who gained 40 lbs (of mostly muscle). Here's my input: I've been skinny all my life and I recently got some help from a friend of mine who's a successful weight lifter. I bulked up a bit this summer (+20 lbs from this time last year). While I'm still skinny for my height and not particularly strong, I've gotten many compliments about my gains. I know it's wrong to be approval-seeking, but I can't help but have gained some inner confidence here.

TL;DR - Self-improvement is an easy way to build inner confidence.

Second, I've been watching some RSD videos on youtube. Tyler occasionally talks about being unreactive or "icy". This has really helped me a lot in conversation. Before, I would nod in agreement, smile, and say trivial things like "cool"/"interesting" way too much. This probably came off as unattractive and 'beta'. Also, I wouldn't have any substance in my responses because I would rush to come up with some forced answer. Plus, speaking slowly shows confidence.

TL;DR - Be less reactive in conversation. Take your time responding.

Go out! I turned 21 earlier this year but had never really explored the bar scene because I was uncomfortable there and didn't enjoy myself as a result. This summer I was working in my college town and since there weren't as many people around throwing apartment/house parties, the only real social scene was bars. So, I pretty much forced myself to go to bars at least 3 times a week. If you want to get better at something you have to challenge yourself. Challenge your comfort zone and force yourself to go out and get experience.

TL;DR - Go out as much as possible. Just do it.