By Mikal E. Belicove|For entrepreneur.com|February 21, 2012

It used to be that advertising on Twitter was limited to large companies and brands that could afford it and with whom the microblogging platform chose to work. But come late March, any business or brand — regardless of its size — can promote their product or service on Twitter by using a new self-service tool similar to the ones offered by Facebook and Google AdWords.

To kick things off, Twitter announced a partnership with American Express late last week to give the first 10,000 eligible Amex merchants and cardholders who sign up online initial access to the advertising program. Amex reports that the program is still open to interested businesses. All other businesses are expected to be able to advertise on Twitter by late spring or early summer.

Before you sign up, however, it might help to know how your message might get across on Twitter. Advertising on the mircoblog falls into one of three distinct offerings:

1. Promoted Tweets — messages that businesses have paid to promote at the top of search results on Twitter.
2. Promoted Trends — paid placement of a topic in Twitter’s Trending Topics list.
3. Promoted Accounts — paid placement of an advertiser’s Twitter handle in users’ “Who to Follow” widget and page.

So, is Twitter a good place to spend your advertising dollars? Investors and businesses seem to…

Continue Reading: Twitter Makes Room for Your Ad Dollars