The idea of varying your openers is something you need to employ with you are in a scene like a night club or a party. Any situation where you have a group of people in the same venue where you will be opening multiple groups. It is very important to vary your opener so that you aren't blowing out the whole venue with the same opener.
The other part to this is that in a smaller tight knit environment you might open people part of of a larger group with the same line. We don't want people to think you are just giving lines out to people that you meet. That won't work very well especially if there is a tighter social circle there. Plus it will ruin you if they are regulars. You could even risk a previous set hearing the same opener being used on another group.
Study multiple "types" of openers to use while you are out. My openers vary in style but all work for me.
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Direct- "I saw you over here and I wanted to come see what you're all about. I'm Jon." OR
"My friends are having a boring conversation. Consider this like a real life Facebook friend request, I'm Jon."
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Indirect- Insert whatever opinion opener, talking about sports, or whatever.
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Situational- This is going to be on the fly, you just have to be on your toes.
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Kino- I like Gambler's style with these. I got this on his Ultimate Natural Game Disks. You basically use a light touch with the back of your hand on their arm to turn them or lightly guide them. This works very well. Take a step back for calibration so you're not in their face and then roll with your opener.
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Compliment- AFC Adam explains this really well. In the idea that if you are using a truly "sincere" compliment it works very well. Generic compliments like "You're cute" or "Nice Dress" will just get you a basic, "
Thanks 
" and that is it.
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Body Language- Using things like eye contact, come here motions with your index finger, making faces, Middle Finger flips, etc. These are sometimes the best openers. Especially in noisy clubs or if you have some distance between you two.
*Remember saying something is always better than saying nothing* ~ Sinn
One moment you might here me saying,
"You have a pretty friendly face for a place like xxxx. I saw you over here and I wanted to see what you're all about. I'm Jon." Then the next you might see me using my finger in a come hither motion or even the "bird" to get a girls attention to come talk to me. After that I mean look over my shoulder to see another girl and say to her,
"Hi. I don't think I know you... I'm Jon." (This is used after I've established my social proof some).
You have to be able to bend and flex when you're out working lots of sets. By floating from the various types of openers it looks to be much more natural and also feels more natural as well. I encourage you if you are starting out don't just study indirect opinion openers. Don't just study direct openers. Make sure to vary your art forms so that you work to be more natural. Having this ability will also make it easier to merge sets which is not something talked about on the forum much, but is very fun to do.
If you are always using an opinion openers its not going to always work. Later on your ability to vary your openers will help you determine what to use as you better develop your calibration for being in field. There are some girls I know I need to be direct with and others its best to start out indirect with. How can I tell? It's in essence a cold read based on my social calibration of going out and approaching for the past two years.
Don't limit yourself to one form of opener. Have an open mind and vary your openers. When you do your results will increase.
Jon
CHAT
It helps tremendously if you are locked in. This is a big part of this, you need to be stationary. Also, she is going to have to see you doing this as well. So at times I might just yell out "Hey" to get her attention. She'll see you beckoning her, and you definitely have to maintain solid eye contact as she approaches. 
