When should I kiss my girlfriend? We know each other pretty well. I asked her how fast/slow she wants the relationship to go, and what are her boundaries on like kissing and stuff, and she said she doesn't mind. We have both never kissed anyone before.

Ahh, yes... The first kiss. 

Well, as important as it is... "IT" needs no planning.  That opportunity should be taken when the opportunity arrives.

If you put too much thought and planning into it... Then 'it' becomes a 'thing' (which is awkward and uncomfortable).  A kiss shouldn't be more than it is... And what it is... Is a show of affection.  So when you are ready to show her, and you think she is receptive... Then plant one on her.