There are a number of different elements which you should consider when selecting a domain name for your blog, presuming that you are deciding to host it yourself and it is not integrated into your current website.
For a Business Blog, I would always recommend that you host it yourself rather than hand control over to a hosted service. If you decide that there is more benefit in separating your blog from your own website, then having a suitable domain name is important when it comes to branding and developing both reputation and credibility, whether you are looking at a company, sector, service, product or individual niche.
Some of the elements that you should consider when making a decision are:
There may or may not be a suitable mix of these elements and so what you will need to do is find a suitable compromise so that you combine the points which are most important to you. These should be based on the aims of your blog and also your target audience, two key elements of the planning process you should go through before setting up a business blog
Dont forget that you also need to find a name for your blog, a title which is automatically incorporated in the “Title tag” in some most systems and certainly in WordPress. You should always make sure that you use any opportunity to publicise the contents of your blog and so the tagline of the blog is also important as this appears alongside the blog title in specific search engines such as Google Blog Search.