I haven't bothered to sign up on mailing lists for ages. I keep up with the doings of artists I like through their websites and with what is going on in a 40 mile radius from our local publication "Folktalk" on paper or on line and our local radio station.
For our local events I only book artists I have seen live and who I think will go down well with our audience. I've broken this rule only three times to book artists on the strength of an unsolicited CD sent through the post. Two of these were very good moves and the third wasn't. I always listen to CDs and pass them around our committee but out of hundreds only three made it pass the "see live first" barrier!
I always try to get our booked artists featured on local radio station and encourage them to send a CD. It may not affect the turnout on the night but it does raise the awareness of a wider audience and have more effect further down the line.
As to getting bookings for ourselves, we try to visit as many clubs and festivals as possible. This does lead to bookings, but we have also fallen into the trap of visiting the ones who seem to like us quite often so they don't need to book us!