[codeonfire]

One. There is no rule saying that if you get a better offer a few days later you can't take it. That's business, just don't sign anything until you are sure. Less experienced people will tell you about how you should ask for time to consider all offers, but the reality is that if you don't accept an offer within a day or two it will look bad for you and the person extending the offer. It is in fact better for everyone to accept the sure deal that you want and then back out later if a dream job materializes. Also if you have an offer you need to communicate this to places you've finished interviewing for so they can speed up their offers.

The exception is if you just graduated from college as the market for new grads is different. In that case it is expected that you are at a crossroads.