I'm not going to give you a set number of times per week or anything, because every guy will be different. What I have for you is a GUYCALL ALGORITHM, which can be used to determine when, where, how, and why (but mostly when) to call a dude.
Essentially, it's tennis rules: you can't lose as long as the difference in your scores is no greater than 1. So if you've called him and he hasn't called you back, you've just got to wait. But you never need to wait to return a call, by the same logic.
Naturally, some exceptions can be made. A text or Facebook message doesn't equal a full call, but enough of them can be even creepier. And there's no limit to the number of times you can attempt to make contact telepathically.
I'd also allow a double call--calling when you've already called most recently--if some amazing event had transpired or new information developed (ie, a secret pizza party is imminent) in the interim. But don't abuse the privilege.
Of course, none of this applies a month or two in...just during those delicate initial stages when you're trying not to crush him with your immense love or freeze and wither him with your icy indifference.