First, Top 10 Business Blogging Best Practices lays out some general good advice. Here are a few tidbits:
Don't restrict blogs to the marketing department.
Make sure blogging is a good fit for your industry.
Read the blogs of customers, partners, and competitors.
Don't sound like a press release.
Blog about things you know and care about.
7 Best Practices For Corporate Blogging To Keep You Out Of Trouble, meanwhile, offers tips to keep in mind as you try to ease your company into the blogosphere. Here are some samples:
Make sure you post a disclaimer and limitation of liability.
Create blogging policies to keep trade secrets secret and personal lives personal.
Make sure the blog is consistent with the impression your company wants to make.
Following these tips isn't enough to make your blog great. But as MindComet says, they should help keep your blog from getting your company into trouble.