Well, basically it starts with the initiation of kino, id assume, which escalates as your conversation progresses, and after you state your intent to her, that you find her sexy and that you are infact letting her specifically know that you do see her as a sexual interest, she will feel comfortable showing you her sexual interest as well. Now, thats not sexual tension per se, but its clearly a prerequisite for it. Now the tension part comes in when you have a barrier to bounce this off of, like the fact that youre in a public area where you cant just rip eachothers clothes off.
If that makes any sense... :< ? Maybe some other and better explanations will come along to help you out

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But read the ebooks, see how they explain it, and go out and give them all a try, see what fits you, and try to understand the underlying concept of what works and more importantly WHY it works.