My daughter went to college in a different state. We made a deal that she would call every Wednesday evening and every Sunday morning. Ten years later, she lives on the other side of the country, and she still calls every Wednesday evening and every Sunday morning. I can't stress how important that is, on many levels.
My son went to school locally and lives just a few minutes away. We never made any deals about calling since he was so close. It turns out, he almost never calls, and if he does it usually means he needs something.