Twitter - How Do You Build Your Followers?

So we've been Twittering here for a few months working on building up some brand recognition on a couple of new projects and im noticing that we're actually starting to stagnate when it comes to having new Twitter users follow our posting.

Do you folks that have your own Twitter account have any tips or hints on how we can grow our Twitter following further, right now we're up to around 280 followers (give or take) and they actually do all appear to be 'genuine' people not bots.

Any advice you can share on how we can attract more users to our Twitter accounts?

Regards,

Lee