"Does this smell like chloroform to you...?" 
I kid, I kid!
Seriously, though:
1. Figure out something fun you think she'd like to do (that you also want to do)
2. Do the thing with her (while being yourself)
3. If successful, repeat steps 1 and 2
That's about it. We tend to psych ourselves out and put way too much pressure on ourselves when it comes to this kind of thing. Just relax, be friendly, and go for it.

I kid, I kid!
Seriously, though:
1. Figure out something fun you think she'd like to do (that you also want to do)
2. Do the thing with her (while being yourself)
3. If successful, repeat steps 1 and 2
That's about it. We tend to psych ourselves out and put way too much pressure on ourselves when it comes to this kind of thing. Just relax, be friendly, and go for it.
"I was thirsty for everything, but blood wasn't my style" - Live, "Voodoo Lady"