This is your last chance before reproduction. That is the easy part. That is what you do anyway. Get to know some then, they can be your best friend. So promo is huge.
Some bands do mailing lists and posters.
I found a couple of agents. They get a piece of the gig, they get the airplay, they set up the gigs. Well, ok, there is a bit more to it. But if you are short on charm - look for somebody to help you get exposure. Also - don't be afraid to go to the local record stores.