Most of the brands start their social media campaigns with setting up accounts on Twitter and Facebook.
If that is what you have done and sitting back thinking what you need to do next. Here is what you need to do next. Start filling these spaces with relevant content (relevant to your users) and start interacting with the users who come foreward to interact with you in these spaces.
At times, initially for sure and also when your community starts growing, invite them to become a part of the community, offer any benefit if you can, like opportunity to have a first look at products. Once in a while ask questions to seek opinion and help.
The idea is establish yourself as somebody who cares for the consumers.
How are you doing it?