If you want to promote your Brand or Website then Twitter is very god option but for better results you must have enough numbers of Twitter Followers. Getting Twitter follower is very easy, go to twitterholic.com and analyze profiles which are getting good numbers of followers daily. Once you identify those profiles then check their Following and followers ration. If that ration is normal (around 1:1.5) then get their Followers list and start following people from that list.
Be sure that you are not following huge numbers of followers in s single day otherwise Twitter will suspend your account. Best practice is to follow around 300 people per day and then you will get around 100 followers daily. Normal Follow back rate is around 30% but if you using good and updated profile then you will get more twitter followers. If you will follow this strategy then you will easily get more than 5000 Twitter Followers in a month and i think that is very good number.
But for better results, try to get connected with your followers otherwise nobody will read your update and your all efforts will go in vain. So try to be more and more in conversation with your Followers and reply to their post. Once you will start doing this then they will take you as a very good community member and you will get benefit from Twitter.
There are many people who Buy Twitter Followers from companies which provide Twitter Marketing Service. But I like Newmarketingsense.com as they follow all Twitter Guidelines and your account will not get suspended. You can buy twitter followers as very less pricing.