As someone who went through informal rush, I've got to give you my 2 cents worth!
Informal rush is much more casual and nowhere near as complicated as formal rush. It's much easier to get to know the sisters in the house, since everyone is more relaxed, and you're not on a tight schedule.
Most houses will advertise when they're having a COB event (COB=continuous open bidding, which is just another name for informal rush), or you can call their houses and ask for the VP membership and find out when their next event is. You don't have to be invited, but you should let one of the sisters know you're coming, since if they don't have any PNMs coming the event may be cancelled.
Events are a lot more fun than in formal rush, too. They include things like karaoke night, or going out for ice cream sundaes.
Hope this helps!!
Lindsay
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