I have not seen a definitive answer yet. It is supposed to be whatever a girlfriend would do such as kissing with tongue (I think that should be the minimum). But if she kicked me out of her apartment like a real goodfriend would from time to time, I would not return.

I would say the general concensus is a girlfriend type attitude instead of business like. A GFE would, as mentioned kiss with tounge, but not just limited to that, she would in essence act like she had known you for years making you all the more comfortable. I guess what Im trying to say is, its not just what she does but how she acts also. I had seen a few providers prior to discovering TER, but the Lady I met through TER was a true GFE in every sense of the word. Since no one has bothered to mention it yet I'll do it. This isnt a sales pitch either I stand to gain absolutely nothing  by telling you this other than to help a fellow newb as I was helped. Buy the VIP membership so you can read all of the review, this can give you the information you need to see if that type of experience is what you want.
My 2 cents ok ok ok 5 cents
Nervestrike