Our school has informal recruitment in the fall for sophomores and summer freshmen who have achieved grades and such. In the spring, we have deferred formal recruitment for second semester freshmen and anyone else who wants to go through. The fall period is done during a 2-3 week time, and each sorority has COBs, with a defined bid day at the end. In the spring, it's about a week long, and done with all the formal recruitment rules, etc. After formal is done, we have 2 weeks of COB for those chapters not at total, which is pretty much everyone.
dardenr, often times women will wait to go through informal in the fall so as to avoid the hassles accompanied with formal recruitment, but panhellenic is supposed to discourage women from doing that if possible. I know many a girl who thought that they knew the sorority they wanted and waited to go through informal, only to end up depledging and having to wait a whole year to go through again. I highly recommend formal recruitment if you are eligible