jimr451 - 7:48 pm on Jan 31, 2013 (gmt 0)
First make sure you are posting "useful / interesting" tweets - not just promoting your business. People will follow you if your feed is interesting to them. Once you think you have that down, make sure you make your customers / prospects aware of your tweets.
Also, re-evaluate if Twitter is the best option for your business. It may be that your clients are more geared toward Facebook or standard email newsletter.
Hope this helps a bit.