Never look clingy, too exited, just remember, cool, calm, and collective. This will help you quite a bit. Show her you are interested, just not over interested. You want to give her the impression that their are other females that can be interesting, besides her, without verbalizing it, or starring too hard at other females.
When you decide you have found dating girls that you are going to go on a date with, smile often, and listen allot. You should ask many interesting questions, but nothing too personal. Offer a little information on your self. You may give more information later. Remember, that a lady loves to verbalize.
After you have followed the steps above, you have charmed her just enough, to make it just right. You may then proceed to taking her places you will both enjoy, and just have fun. Later you may do things like surprise her with special gifts or notes to let her know you are thinking about her.
Never over do it, though. You should never over do it though. Communication is very important to a lady at online dating service. You should have good communication and listening skills, never forget this. Best of luck to you!