When I say ‘ask’ for her number, I really mean ‘tell’ her to give it to you. You need to take a dominant lead at this point because most women will feel nervous about handing over their contact number to a strange man they just met. If you give her the slightest opportunity to go with her gut feeling she will flake on you. Avoid questions like ‘do you think I could get your number’ or ‘do you fancy swapping numbers’. Such statements are weak and make it too easy for her to reject your request. When you go for the number, hold strong eye contact and without breaking that contact say ‘you seem like someone I need to know better, give me your number and we can meet up sometime’. If she hesitates you may need to assert your dominance further. When girls have ummed and erred with me I have cut them off before they had chance to say anything by firmly saying ‘stop, just put your number in there now’. If she still refuses, don’t push it and certainly don’t beg. Withdraw the offer with something like ‘jeez and I thought you were cool’ and end the interaction. Leave her feeling like she messed it up rather than give her the opportunity to fob you off with an excuse and steal your power. Remember, “I want you but I don’t need you’.