[Alumiyum]

As for the sweat pants problem, have a meeting to specifically discuss what is appropriate to wear when. It would be reasonable to require a certain kind of dress for recruitment events, like "dressy casual". Outline exactly what is appropriate and show examples. Remind them recruitment events are interviews and while they might be fun or relaxed, they should still be treated as special events.

Just make a list. This is just an example...

What is ok:
-Skirts (that are appropriate...decide what length is ok for your campus)
-Dresses (Same as above)
-Nice pants, like black pants, khakis, tweed, etc. (And nice jeans without holes or rips if that would be appropriate on your campus for an event)

What isn't:
-Sweatpants
-pj pants
-items with rips/holes/stains
-items that are extremely revealing

Good hygiene and grooming is also important. Clean, brushed hair is important. Hand out mints before events. If they happen to wear make up, remind them to make sure it isn't TOO out there (nothing so extreme it's offputting). Remind them to make sure they have clean nails. Have a couple of sisters wear outfits you've seen before and know are appropriate as examples. It's important to avoid calling anyone out or putting anyone down, of course.

You could have a "What not to Wear" event and watch an episode of the show with some popcorn or something to start off the meeting so that it's fun. Plus, Stacey and Clinton do a good job of explaining that how you look does matter (without being ridiculously nit picky or going overboard and making it life or death), because it says something to people you come into contact with day to day.

Have members wear letters around campus on certain days (say every Wednesday), and find out if any are involved in activities on campus outside of your sorority. Promote that and encourage them to wear letters to those events when possible. Have a meeting devoted to practicing conversation for recruitment events. You might also have a "pin dress" day once a week or once every two weeks when members wear their pins and dress nicely. These are all ways to better prepare for recruitment events...visibility before the events is important as is good conversation during.