rush/bid process

So tomorrow is the first rush round. When will frats tell freshman that they are getting bids? If you are invited to the second round, does this mean you’ll probably get a bid ?

I have heard of people already getting prebids, but will I find out tommrow from some frats? Also, if I have only hung out with a frat a little bit will they invite me to their second round or is it for only kids they know will get bids?