Hmmm..Well, to finger someone, you have to get them very turned on because when this happens, their "hole" opens up because from excitment. The more you excite them, the more wet they will get and the more their hole opens up. Also where their hole would be is where you will feel the wetness coming from. A girl has 3 holes down there---the pee hole, the ****** hole, and the *** hole. The vaginal hole would be right under the peehole but be careful because if you accidently slide into the pee hole it could hurt her a bit.
Once you find the hole, just slide in and she will know when you are in because she should feel pressure. You youself will feel your fingers enter into an opening. And then the same goes for you when she does it to you. Then from there enjoy.
Another kind of advice i have is: if you are both virgins, there would be a "curtain" where the ****** hole would be. You would break that when you finger each other. But let me say that if you both "pop the cherry" then there will be blood but it's not a bad thing, it's just your virginity.
Best techniques? hmm.. i'd say let her tell you what to do. I mean, unless you really want best techniques, just search on the internet there should be some.
If you have any other questions let me know.