which Twitter site is best for twitter users?

Don't really understand your question but I mean if you are intested in Sports you can try making a sports page.
What is popular now is something like sports vines, live score twitter etc.

Your question is not clear but you can create a niche related account and get the follower in the following the under mentioned steps -


1. Create a Flashy Profile Picture.
2. Give a meaningful and a solid Bio.
3. Have a Flashy Background which displays your message.

Once you have done these steps let's move out to the world-

1. Search for your niche in search box - like internet Marketing
Ok
2. Now find out someone from the list who has lot of followers.
3. Go yo his Twitter account.
4. Follow his followers to the tune of around 40 in the beginning and later can scale up. Do not be aggressive as that ruin your reputation as your followers must me more than your following always and have a long term prospective if you have 40 followers in a single account daily then it is like 120 targeted followers for you in single day. So be patient and follow this rule.

Ok

Post so equality tweets. You must post 2 out of 10 tweets which has a link to your squeeze page.

The Most Important Part - You should work like a solution provider. Do not run after sales initially just build relationship first and ten sales will automatically happen and money would flow automatically

I hope this solves your problem.

Are you asking what kind of plugins or extension for twitter. Extension and plugins help you to track new tweet/staying in touch what was happening without open your twitter directly. You can used TweetDeck, Yoono and etc...

Well I will recommend you to don't try to grab followers automatically, as it will give you so many spam users and ultimately you will find no good result.