Getting business or click-through on Twitter is like most social media platforms (or even face-to-face networking). If you constantly spam people, only post links to your website, don't interact with others, etc., then people won't follow you, will block you and possibly even report you for spamming.
You need to build up a rapport with people, just like here on UKBF. If you're friendly and approachable, you help people when they need it by answering a question they put up, if you retweet messages you think other people will want to know about, etc., then you will get quality people following you, and it should always be quality over quantity.
Remember, depending on what phrases you type in you may get people auto-following you. I found I was being followed by a chainsaw firm in Texas, and I couldn't think why. Then I remembered I had tweeted about going to an event and "you could cut the atmosphere with a chainsaw". Obviously this firm had set up Twitter software to follow anyone who tweeted about chainsaws! Not to mention the people that spam you if you so much as mention iPhone, iPad etc.
Treat people on Twitter as you would if you met them face-to-face and you won't go far wrong. You'll build up a great reputation and people will start asking about your business, etc., and then even buying from you.