Communicate: Discuss ahead of time how you will communicate regularly with your student (e-mail, phone, letters, etc.).
Get e-mail and learn how to use it.
Find your best calling night, usually Sunday, and ask how often - call without an agenda sometimes.
Send great gossipy letters to your student about high school news, sports, and hometown trivia.
Consider buying your student a cell phone.
Send family pictures, videotapes, audiotapes, funny cards, or clippings from your hometown newspaper.
Making and sending care packages that are really personal can be so much fun - like playing Santa (and often leads to a social gathering in your student's room).
Don't be shy in communicating how much you miss your son or daughter but do refrain from emotionally unloading.
Go to Family Weekend if at all possible. (Or - Decide with your student whether to attend parent's weekend. Lack of interest may be interpreted as lack of caring.)
Discuss good times for school visits...homecoming, basketball games, etc... and plan them.
Celebrate and Remember this Milestone: For Everyone
Identify a ritual/ceremony that celebrates this rite of passage for your student and your family. An intimate visit to a favorite family vacation spot, a family party, or even a large neighborhood block party are some examples.
Save the e-mails and bind them for that graduation party.
Take lots of pictures...of their roommates...friends...packing...etc.
Write a letter before they go off to school about how you feel about them, their leaving, their accomplishments, them growing up.