I think the best idea is to be patient, don't get too depressed or discouraged if your social life doesn't bounce back right away. If you're just starting back, then you have to give it some time to reconnect with your old friends and make new, and possibly better ones. Maybe make some time during the week to go out for coffee to reconnect, or even have a mini study group with new people in your classes. I think that if you start out with little outings like that then your weekends may fill up, but until then, stay positive and keep working on your grades and I am sure people will love to be around you. ;D