Step 1 - register your account on Twitter
Step 2 - go to Twellow.com to find people with similar interests, i.e. Online Marketing
Step 3 - Once you have found the person you are interested in..say...hmmm Frank Kern, simply click on his followers then begin to follow them....click on a max 400 per day otherwise Twitter will think you are a bot. Do that for the next couple of days until you reach your max 2000 that you can follow.
Step 4 - go to Your Twitter Karma
and follow the instructions...don't worry about having to enter your twitter name and password etc..it's safe I have already checked it out..fully.
This site will tell you who you are following and who's following you. It's a bit clunky (api issues i guess) but you can then unfollow those who aren't following you. This will allow you to go back to step one and add more followers. ***edit***Wait a few days before you do step 4 to allow those who you have recently followed to follow you a back. If after a couple days or even a week then you can stop following them.
This will allow you to get past the 2000 mark that are following you and take you to that next level on Twitter.
Hope That Helps,