Success on Twitter hinges upon interesting tweets or linking to great relevant content.
Focus on one vertical Market or subject area otherwise you will dilute the level of interest. People unfollow if you tweet too often or your subject matter is too broad and irrelivant to them. If you want to tweet about several topics, create another account and build several personas.
Maximise the chance of a follow make sure your profile is completed and your web address is supplied. People will use your profile as a factor influencing them to follow you. If you are targetting a specific location make sure this is present also.
Tweet relevant and quality content but not too often. People will unfollow you if you spam or waffle.
Try to anticipate when your target audience are on Twitter. Tweet at this time or use a service like Hootsuite to schedule tweets.
Aim to be retweeted, if someone reteets you they are republishing to their followers. Not only does this broaden the message reach but also opens potential for gaining new followers.
Follow people but manage this process carefully, never follow substantially more than follow you. This looks bad to those evaluating you worthiness. When you follow someone, in most cases they will be informed by email. The hope is that they will follow back. This method invariably will result in gaining followers.
Find new people to follow using search.Twitter.com . Location and keyword searches will deliver potential individuals.
Inspecting the followers and following of other users relevant to your specialist area are great feeding grounds when mining for people to follow.
The #followfriday or #ff tag convention is used on Fridays to announce users in tweets which people this are worthy of following. Use this to recommend people in your Market, the likelihood is some people will return the favour. #traveltuesday is a similar tag for travel tweeters.
Engaging specific users with influence or large followings by sending them a public message makes them aware of your presence. Make it relevant, they might follow and their following might mimic. A follow from an authority in your field is like a real world endorsement.