Most Helpful Girl
don't put too much tongue
if you haven't done it before, follow her lead: see how much tongue she puts in and do the same
also: try doing some slow circles with your tongue around hers
Most Helpful Guy
It definitely depends on your girl. I would suggest you just be open about it while you're kissing. Try things and ask her what she likes, or ask her to demonstrate it for you. That is definitely best and both of you will appreciate it later. However, if that would be too embarrassing for you, I would suggest going nice and slow with your tongue. Definitely don't be too aggressive unless she specifically tells you she likes that. For the most part you can just slowly trace her tongue with yours or along her lip as you hold it between your tongue and upper lip. Lastly, you don't have to specifically focus on or overdo the tongue. It's nice sometimes as a complement to your kissing, but be sure not to neglect kissing with your lips as well. What's best is a good mixture that happens naturally when you are both able to relax and not be thinking about it too much. Hope that helps you out, good luck!