When I set up a blog for a client, I am the default user. So all pages and post initially appear to be written by me.

No big deal, until the theme you use supports gravatars. Then my gravatar shows for all the posts and pages.

Manually changing each post is not a big deal in the beginning, but once the blog gets going, it can be a tedious affair.

Until I discovered a little trick. To update the authorship of a number of posts at once – go to the Posts >> Edit menu

Using either the check box at the top of the editor, next to the word POST, or by individually selecting the posts you wish to change, check the boxes and then click on the Bulk Actions drop down menu and choose Edit.

In the third column will be a drop down menu for Authors – simply choose the new Author and then hit the blue button that says “Update Posts” on the right. Voila – you are done!