On Twitter, your followers equal your audience. Although follow count isn’t everything, generally, you would rather have a follower than not. Also, when you follow someone and they follow you back, the likelihood that you two can have frequent conversations is far greater than if you didn’t.
So how do you get someone to follow you? Well, you already know the basics–have a real profile picture, fill out your bio, etc. But once you’ve actually set up your account, you have to let people know you exist. By default Twitter sends email notifications when someone follows you but most avid Twitterers turn that off to avoid email apocalypse. So unless that person checks their follows every day, they don’t even know you’re there. Even if they know you’re there, most people don’t go through every new follow, check their bio, review their stream and then follow the people they’re interested in.
But even if you’re the best thing happening on Twitter, the easiest way to get someone talking to you and probably following you is to say hello. As soon as you follow them, send them a tweet that says “Hi, I just followed you and this is why.” Then strike up a conversation. Answer one of their tweets. Ask them a question. You’re more likely to get followed back than if you just followed them and left it up to them.