How do I get more Twitter followers?

[One]

I saw that some sites are ''selling'' twitter followers, so I was wondering if there's any site where you can get twitter followers for free by registering yourself...?

[Sailor...]

You can grow your twitter follower naturally by twitting many different interesting things,by following others. Besides, you can try twiends.com where you can grow your follower for free. just log in there with your twitter account, allow twiends to access your account. Choose your desired domain like technology, sport etc. You will see a lots of twitter profile with seeds. You have to follow them and you will get similar no. of follower as seeds of that profile.