Membership Management

I joined my guild a good while ago and was promoted to Leader, but the original founder of the guild dropped out of the game. Currently I am more of less leading the guild, by default of being the primary person to initiate Raids. I would like to be able to promote some of the more productive current members, but cannot determine how to do so. The guild is not performing at a very high level because we seem to have very new players, except for a very few of us, and I would like to be able to reward good performers and cull non-participants.