Wait Caylaashley - we're talking about the vital parts of a college experience like cheese and haunted dorms but you want to talk about something silly like sorority recruitment!

. Okay then, back to that.
Please keep in mind that as I said, my daughter went through 4 years ago, so this information may be dated. Your best source of information is the Greek Life Office and the site CougADPi gave you.
Having said that- when she went through the schedule was Day 1: Orientation, Day 2 and 3: Open House (You go visit all of the houses and its split up over 2 days), Day 4: House Tours, Day 5: Philanthropy Day, Day 6: Preference and Day 7: Bid Day. On Bid Day the girls normally went somewhere (water parks, camping, river rafting, etc) with their chapter. I'm not sure what happens now because this used to happen on Saturday and then traditionally they would go to barbeques that all the fraternities held on Sunday, but now Bid Day is on Sunday I think.
There was no particular dress code (in the "You must wear a dress on Day 2" sense) when she went through. She wore sundresses most days, shorts (nicer pair I think) one day, and maybe capris one day(think those have gone by the wayside). Preference is more dress up. I was helping her move in the day recruitment started her freshman year and we also saw plenty of jean shorts and lots of skirts. Of course, this could have changed. They should send you out information after you register for recruitment that will give you the schedule and general ideas about what to wear.
By the way, not sure if they are still doing this, but WSU's Greek Life used to do a fair type of thing for one day in Seattle (usually Key Arena/Seattle Center conference rooms), one in Spokane and I THINK one in Vancouver. These are in the summer. Each sorority has a table/booth set up and girls from that sorority there to talk about it and answer questions. If they still do them - go. It's a great way to ask questions and meet some of the girls in the sororities.