When I was a collegian, our Director of PR would have a PR woman of the week. Other sisters could nominate people by writing down their names and reasoning and putting them in the director's box during the week, and then she'd pick whoever was doing the best job of representing DG on campus or in the community for that week. For example, if a sister was nominated to Homecoming Court, acting in a play on campus, or heading up a committee for Relay for Life, then her active involvement in other areas would reflect well upon our chapter. Whomever the director: PR chose would get some kind of reward, usually just as a gesture of recognition and a pat on the back to keep up the good work.
Also, they'd remind us at chapter on a frequent basis to always make sure we represented DG in the best light...you could include a reminder in each week's Anchor Line, with little tips like "Remember to wear your letters to class," "Only wear your badge with business dress or nicer clothing," "Don't engage in any degrading conversations about the Greek community or the previous night's activities while wearing letters," etc. Little things like that which seem so obvious, but can make a world of difference in the public eye, are good points to remind the chapter of to boost your PR.