I’ve noticed that the first stage of attracting followers on Twitter (beyond your actual friends) is that accounts that act like bots start to follow you. Not to name any names, but one of my followers is just reporting random things from Google News, another one is just throwing out facts and observations about dog behavior.
The custom on Twitter seems to be to try to follow those people who follow you. I’m doing this, but I’m making sure that the people I follow seem like real people before I follow them.