Okay man, from what it sounds like, it sort of sounds like your going in with High energy regardless of their energy. This basically means you can't establish quick rapport with someone that you approach, and quick rapport is something that is vital to carrying an approach (without rapport, you can't hook a set).
Rapport is like a dance man, to dance, the Male is expected to lead (being the dominant one), and the female follow, but before you can lead - you must have a partner. Therefore you and the person you are approaching must first meet on the same level, and from there you can bring her up (high energy) or down (low energy).
A simple way to create rapport is to meet at an emotional level (most people can pick up some queue of their emotions from their facial expressions - sensory acuity) and enter with the same sort of emotion and energy. The other way to quickly establish rapport is by matching and mirroring their:
-> Posture: or Bodylanguage, how they hold themselves - are their arms crossed, hands clenched, are they slumped over or are they standing confidently, etc. etc.
-> Gestures: what they do with their hands when they talk, if they move them around a lot and move them wildly, or in contrast, don't use them very much.
-> Facial expressions and blinking: If they smile, you smile, if they blink, you blink, it creates really simple and quick rapport because you guys are connecting on a subconscious level.
-> Breathing: keep tempo with their breathing, if they begin to breath fast, you do the same.
-> Voice Tone/Tempo/Timbre/Volume: Obviously some of this one isn't relevant to pickup, however, talking at the same volume to them, in the same speed (fast v slow) and the fluidity of their speech is a great way to connect. You'll notice this one especially when you're talking to someone that you're in deep rapport with, like a good friend .
-> Word Predicates & Key words: You can find a list of key words, etc. at
http://www.kvaes.be/nlp/representationa ... aesthetic/ although that does get a bit more complicated.
-> Common Experiences and Associations: This is a simple one, just relate an experience of yours to an experience of hers.
Obviously some of these can be used earlier on then other, e.g. Breathing / Posture / Gestures / Facial Expression (to a degree) can be seen from a distance and yours changed, others like Voice Tone/Tempo/Timbre/Volume and Word Predicates + Key words are used in mid-rapport or when you've been talking for a while, and common associations can be used whenever.
Hope this helped!
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Secondly man, you mentioned this at the end of the post, that you imagine like those people think that they're too good for you, etc.
That isn't it man, they might be in a rush, or you might have to work on your delivery - start your opener in a louder, clearer voice and stay still once you've began it. If they walk away, too bad for them, they're missing out on talking to you, and you can just move straight on to another set.
I would also look into some inner game stuff, because it seems that you considering that they're thinking that speaks to an inner game flaw of your own. The best (in mine, and a lot of other peoples opinions) product out at the moment would be the RSD Blueprint Decoded. If you have time, take a look at that.
Best of Luck!
~JR*