You should locate people in your target audience and begin conversing with them. Think of Twitter as a place to have discussions and express ideas, not just a place to promote something. Take part in discussions, polls and answer questions with quality answers. Become a valuable participant so your followers don't think you are only there to market your products. It's also to your advantage to answer questions because then people start to trust you and respect your knowledge. The more you participate and help out, the more people will see you as trustworthy. Your reputation as someone who is a good source of information will spread to more Twitter members. More people will then check out your profile. Promote your Twitter account - this is one of those marketing tips that people often ignore. Your account is where people connect to when they want to hear more from you so it only makes sense to promote your account. Whatever ethical ways you can think to get followers on Twitter, use them. This is not a step that can be skipped, it is absolutely necessary to promote your account. You can also get it printed on your business card. You have to think out of the box to get new people to follow you. Also, try to build a group of followers who will already want what you have to offer, you will make much more money this way. The key is to go after people who already have an interest in what you have to offer. It's about the quality here more than the quantity. You can also have a link to your Twitter account in your forum and email signatures. This would drive extra traffic and give you a boost in your follower count.
Automation is an element that you can't afford to overlook if you want to get the most out of Twitter. Software such as TweetDeck will allow you to optimize your campaign and stay on top of growing trends. You'd be able to know where your product is being mentioned in the Twitter stream so that you can get in touch with new people and add more subscribers. This is only one tool; there are many more. Do a Google search for any tools that will make things easier. You should see Twitter as a great way to get in contact with those people who matter most. Ultimately it's your choice how you make use of it.