Yeah I know that too, going around smiling and looking all happy is a bit creapy, and you look like a happy clown. Smile at the right moments.
EYE CONTACT:
I really believe that eye contact can be used as attraction.
But you have to understand first that eye contact is visual,
so body language and looks are a bit important here.
Every time I go out, I got confidence, I display it with my body language.
I know girls check me out, some of them are interested, others are not, thats just the way it always will be thats a bit of your life, embrace that fact!
If you take care of yourself, grooming, hygiene ,tanning, nice clothes etc. it will help you out alot, and you will get more eye contact from girls, everybody likes someone who looks fresh.
So lets say im in a club, I never start off with looking at girls and sarging right away (thats a indication on being needy), I let them take notice of me, I start with having fun with my company that I came with, we laugh, get some drinks, and have fun talking/dancing. And all I have to do for myself is being my best self!
Now I had fun with my friends, girls have been looking at me. I haven't looked at them, so all I have to do know is find these girls that are still looking at me and bust them. If I see something I like, I show it to her, you have to be careful of how much you show, you should never give yourself away on the spot, I look, and a smile just a little bit, smiling to much is like saying (I really like you), I save that for the girls I know is easy to get. I smile a little bit, and get back to my company, lets say we get contact again, I either smile again, or I blink with my eye to her, it depens on what my gut feeling tells me to do, If she likes it, I approach her with this line from Keys To The Vip it goes like this "Is it time for us to stop flirting and start talking?

", I like that one because its smooth and displays alot of confidence. If she says "Yes it is", isolate her she has already agreed to talk to you! If she says "No, I got a boyfriend / I was not flirting", I just say "Okay, you looked like you had something on your mind, nice to meet you have a good night

".
IoI's:
- She looks at you from time to time.
- She looks at you more than 3 seconds.
- If she looks and blinks
- If she looks and smiles (but it can also be a friendly thing she does)
All you have to be is to be confident that she looks at you and likes you,
you just have to approach her at some point and dont take to long because you will loose her. I have lost girls because of taking to long, and I have gotten girls by being so mysterious.
I will share 2 of my stories:
I have looked at a girl a whole night, and still gotten her number before the club closed. One girl actually approach me and told me that she was leaving the club, and all I did was look at her sometimes and then stop looking for a while, and then looked back (playing hard to get). I was stupid enough to blow her away by saying okay, have a great night. She gave me kiss and said bye. That was all the talking we did. Another girl came up to me in the smoking corner, and told me to save her from a creepy guy, than right after she said Do I know you?, we ended up kissing and switching numbers.