Invite your friends to participate in the Q/A board (I have one, if you'd like to look). I also did a give-away; more than 714 people requested the UK edition of my novel, and more than 50 added it to their "to read" list. I'm planning to follow up with all of those people when the US edition is available (coming soon!). :-) Best of luck to you.
But has anyone done one of these before on Goodreads? Any advice?