Works for me
Like you said there is no set amount of time. It's like the others are saying man you just build attraction at first. When you first meet the girl build up and flirt and show her that you are interested and hang out just the two of you and after you do that a time or two over a week or two then back off and take that away from her. Make her question why you aren't throwing yourself at her like every other guy always does, it will drive her nuts and make you valuable and unique, and don't call her, wait!, and she'll call you. It may take 3 days or it may take a week depending on how patient she is in testing you; but she will contact you just to see what's up and if you're the real deal. When she does call you and see why you havne't talked to her or to see if you want to hang out, if you really wanna drive her nuts then tell her you that you are really busy all week (thus pushing her off and showing your plans and life matter to you not hers) joke around with her a little bit and at the end tell her you had fun hanging out with her and you'll give her a call once things wind down. Call her after the week and say hey I'm going to do __________ on Tuesday and thought it would be something you're into. You want to join? she'll be eating out of the palm of your hand. I've found this also is your best bet at getting a girl back that flakes out on you. (you should always next them anyways) but if you ignore them and don't try and contact them to fix it and qualify to them and just act like you don't give a **** and you'll get along just fine without them and get out and do that, 9 times out of 10 the girl will re-test you with a message within a month and then you have a chance to take back control from your fvck up. And staying busy to where getting to see you is a rarity is what gets them to pursue, it makes time with you more valuable than time with anyone else because who knows when she'll get it again and she will feel a need to get more of it with you. Hope this helps, there is no set method but this one usually works well for me.