There are lots of ways to earn on twitter.
But to earn, at first you have to gain a smart number of followers. If you follow any one, he would follow you. So follow people who are on your niche. Then publish tweets expressing your business. Thus your business will be prospered. Or you can add your affiliate link on your tweets.
Many websites also give chance to publish another people's tweet and they will give you a commission. Some others also pay you when peoples click on the links provided on these tweets.
If you have any other questions, you can find answer at earn with twitter
