How do I start a blog?

There are a few things you need to remember when starting a blog:
1. You are writing for your human audience not for search engines (these days good quality interesting content is actually what search engines are looking for anyway so these goals are becoming closer in alignment) so make it interesting, make it varied and make it often.
2. Write as often as you can as the only way to build readership loyalty and search engine interest is to create content on a regular basis.
3. Write articles of around 300 to 600 words long. Any shorter and you can't really tell an interesting story, much longer and you run the risk of losing their interest.
4. Keyword inclusion is good, but keyword stuffing is bad. The SEO companies I work with who once would have told us all to achieve between 5 and 10% keyword density (crazy), and now saying that anything over 1% is bad and that what you should be focusing on is synonyms, a variety of words that focus on a keyword theme rather than a keyword density.
5. Find a platform to write your blogs on that is both aesthetically pleasing and simple to use, because you want people to want to read your work, but you don't want it to take an age to upload it.

Finally remember that you are creating an online persona through your blog. Decide your voice right from the beginning, will it be reflective of your brand or a softening side to a very serious business?

Hope that helps.

hmmm you can try Google, there should be millions of sites you can use to blog on, or even guest blog perhaps. The biggest ones seem to be Wordpress and Blogger.