I need some tips. BADLY?

I am 18 and my girlfriend is 17 and we've been together for 3 months. Anyways, we kiss A LOT, but the other day was the first time we had some tongue action. I slowly entered my tongue into her mouth and slightly brushed hers and then i think she got the hint as it happened a few more times. it was subtle, but it was still present. Anyways, obviously this will happen again and i would greatly appreciate some tips. (while me make out there is usually dry humping involved, but she is the good girl type and i don't know exactly how far she is willing to go) so yeah, please just feel free to give me some tips on how to turn her on while making out. :)