Step One - Place something interesting and relevant to your niche in your twitter profile.
Step Two - Use an attractive and niche relevant twitter back ground.
Step Three - Make a list of 4-5 big movers in your niche who have say 10k or more of twitter followers
Step Four - This is the boring but essential part. Go through the list of people following your number one big mover from step 3 and follow 2000 of them. Twitter will not let you follow more. Make sure you don't do more than 200 a day so this will take you around 10 days.
Depending on how well you do steps one and two, at least 500 of these people will follow you back.
Step Five - Unfollow all of the people you followed in Step four. If you want to be careful, unfollow a maximum of 200 a day.
You will lose some followers but not many so don't worry.
Step Six - Repeat steps 4 and 5
My results - I did this process three times and currently have 2360'ish followers that are all very relevant to my niche.
My mistakes - I made mistakes. I did not have a nice back ground until round 3. I only limited the people I followed to 200 a day in round 3.
Boring - This is boring and some what time consuming but you can do it in your town time like when you are watching tv or chatting to people online.
Help - there are a lot of programs/services that will identify the people you are following who are not following and do other stuff. I tried 3 but found they either did not work properly or were not worth the effort.
Next - Now I need to learn how to use this mass of followers to drive traffic and interest to the blog I want them for. Any tips and suggestions are welcome