Encourage them to stay on campus Many students, especially those who live within a few hours drive of the campus, want to come home every weekend. They usually get over this eventually, but you can help them by encouraging them to stay on campus. Of course, you want them to come home occasionally, but discourage them from coming home every weekend. If you don't hear from them for a long time, give them a call. Let them know you are thinking about them and miss hearing from them, but keep it light.
Students do get busy and are notoriously thoughtless about keeping in touch.
That may be all there is. If there is something wrong, give them a chance to tell you, but don't be too intrusive. Listen carefully, be supportive, and remember they will sometimes make mistakes and you can't stop them. When they are ready, you can support them in cleaning up whatever mess they may have gotten themselves into. On the other hand, don't panic when they call home unexpectedly.