A blog is nothing more than an article published online and updated regularly. For a small business a simple blog is essential because it is an easy way of keeping the site up to date and showing you care enough about your business to want to share it.
If you have a modern CMS based website no special website or software in necessary to start a blog. In fact beware of advice that tells you to go out and stat a free WordPress blog or create a micro-site for blogging. Remember the main reason you are thinking of blogging is to improve your business and that means getting more people to your website not helping other brands get traffic to their websites.
You should Blog about what you know and presumably related to your business or brand. Try to avoid the hard sell. Instead share something topical and informative, give the reader something and in return their perception of your business should improve. You can rely on a visitor to seek out more information about you from your website without forcing links to yourself in you blog. Always try to include a picture or graphic,
An effective blog will have the option for visitors to leave comments, encourage this in your writing style. Sooner or later someone will leave a negative comment, Use this as a chance to show you are able to take negative feedback and respond positively. Do not remove comments unless they are clear spam or off top0ic.
You should blog at least weekly, as a minimum monthly. Less frequently that that, remove the blog because the message you are sending is you do not care enough. Always include a date of publication on a blog so people can see it is up to date.