The third strategy is by far the best. There are literally thousands of free websites out there that will link you to free courses. All you have to do is go to the search engine and type in the subject in the search box. After clicking through all the results, you should be able to find free courses from your favorite courseware. If you like there is a link at the bottom of the page that will take you to the free website.
To start doing this just to find a decent keyword search for something relevant. The keyword should contain the word "vote" or "tweet". If you want to get a real large audience, you need to use the keywords "tweet" and "vote". Try using quotes around the words to keep the content relevant. I recommend using quotes around words that have a long tail because people tend to get bored with those.
When you are tweeting you want to post as much information as possible so people see you're more knowledgeable. The easiest way to do this is by posting short but interesting snippets of information. Longer tweets will be lost in the thousands if people don't take the time to read them, but a few short posts can help people remember you and come back to see more of what you have to say.
The second way to gain Twitter followers is by voting on other people's tweets. get twitter votes sounds simple enough, you click on other people's tweets and they show up in your newsfeed. Every time someone tweets something interesting you click on it and make a vote. Every time someone clicks on one of your votes, you gain one Twitter follower. It's that easy.
After you have found some interesting posts, you need to take a little time and write a short bio about each one. In your bio to include where you live, how long you've been studying, and what your goals are. This will allow people to see you as a credible source of knowledge.