what gordongekko said is right . marking activities at twitter aimd to make more pople know what you have said ,and attract them to your site,anyone who want to ttract spider will be faild ! so only really listinner at twitter is valuable !
I think the best way to get followers is to stay active in twitter through sharing links that may be of interest to your followers and interact with them.
Every good/interesting tweet produces a nice amount of new followers and when I promote one of my blogs, theme related to the tweet, some new subscribers too.