Just be normal, blog about the things that interest you not about your company/website. If you discover something useful them blog about it, maybe link to the story but make the post your own.
Do NOT treat the blog as a marketing tool, people will soon spot this and not bother to return.
If you really can think what to say then don't bother with a blog.
Note: there has been some research on post length, 200 words seems to be the minumum, 600 optimum and up to 2000 words is still quite acceptable if the post is well written. Can't find the source at the moment though.