greeneyes,
As a guy who enjoys going down on women, be gentle not rough, start slow and let your passion and her reactions guide you. Use your fingers inside her. Use your tongue both to lick and to push inside her. Enjoy it. Don't focus too much on her clit, it's not a race to see how quick you can make her cum. If you're into it and she enjoys it, play with her ass too. NEVER go from ass back to front with a finger. Once it's in the back it only goes there. Flavored lube may be fun or chocolate syrup, whipped cream. Her reactions will tell you what she likes but don't just do that one thing. Keep changing it up and tease her a bit before going back to what makes her moan the most. Reach up and pinch her nipples and play with her breasts. She may even like licking your fingers while you're playing, again her reaction is key. Basically it's the same rules as making love with anyone. Pay attention to your partner(s) and they will guide you. Don't be a one trick pony and have fun. If something doesn't really work, laugh it off and relax.