Many people and especially men, treat their first call to a person that they just met as a pure technicality – a brief, plain conversation during which all they need to do is to set up the time and place to meet. By doing this, these people are missing out on a very important step in the interaction. In fact, the first phone conversation is very valuable because it can be a great indicator of where things will go later between you and her.
If you have a great time talking on the phone, laughing, teasing each other, exchanging ideas that you both care about and finding each other's company interesting on the phone, the benefit of such a conversation will be two-fold: first ,, you will already be interested and even attracted to the woman's personality since you have already enjoyed interacting with her; second, by this telephone conversation, you will have already "broken the ice," so that your first date will likely be free of that typical awkwardness of the situation where two strangers are meeting and talking to each other for the first time. This will make things easier and more fun for both of you. You will already be more comfortable with each other when you meeting in person because … you are not really strangers anymore.
On the other hand, if the first phone conversation does not go very well, and if you have nothing to talk about, you will likely not enjoy each other's company in person either, and therefore you are probably better off not wasting each other's time and you should not meet at all.
Finding out whether you find each other's company interesting over the phone requires more than a quick five-minute conversation. Therefore, I suggest that you have a fairly long first conversation – around 20 minutes or so to get a feel for each other. Of course, you should not hang on the phone for two hours so that you get sick of each other before you even met, but getting an idea about each other's personality through a slightly longer than usual conversation before meeting is a very good idea.