Getting a woman to give you her phone number without you having to ask for it is a strong indicator of interest.

Asking for a woman's phone number, after you have made an agreement to meet up at a specific location or after having a cup of coffee is an average indicator of interest.

Asking for a woman's phone number, just because she said hi and talked to you for a few minutes; is a weak indicator of interest.

In most cases having a woman's phone number is better than not having a woman's phone number.

However, how you get a phone number can increase or decrease your chances of actually getting somewhere with a woman.

If a woman doesn't like you she might hold a conversation with you, but, she will never ever volunteer her phone number and if she does offer and doesn't like you odds are it is going to be a fake.

On the other hand women will give a man her phone number if he asks even if she has little or no interest in him because it is easier than risking saying no and having to deal with him asking for the rest of the night.

At the same time she might lose a certain amount of interest in a man who she was attracted to when he just asks for her phone number because in her mind every guy asks for her number and part of her attraction was that you were different from every other guy and now you have proven to be just like everyone else.

Now, it is not impossible to actually get somewhere with a woman if you just ask for her number for no other reason than you think she is attractive. Yet, the man who gets a woman's phone number because she gave it to him on her own or there is a real reason for asking for it other than finding her attractive, has a better chance to actually get somewhere with a woman.