Blog is short for Web Log. To get started, have something to write about. What are you an expert in or want to be. Talk about it via your blog. You can even keep your posts private until you feel comfortable in sharing them with the world. I like to follow a write/edit model. I just write without caring how it comes out. Then I go back and fix up what doesn't sound write.
The key blogging sites are Blogger.com, Word Press and Typepad. Also check out some of the top blogs.
Go to these websites, sign up and start writing about something you're passionate about. The followers will come.
I follow a number of blogs on various subjects.
The other thing you need to do is find topics and blog every day. Whenever I come up with an idea for my blog, I record it in a list of blog articles to write in Listi.net
Set aside a time each day to write. Set an egg timer and go for 5 minutes on a subject. Most of the time you'll be able to go much longer. Just be sure to wrap up your article and post it.
Keep your posts short and use Google to learn how to improve and write a blog or get a book from Amazon.com.
Don't try to be perfect with your writing but make sure your spelling and grammar are correct. In the words of Nike, "Just do it!"