I have a content type on my drupal site that anonymous users can create. However, I don't want anonymous submissions to start out marked as "Published" -- they need to be approved before being posted live. What is the best way to accomplish this?
The workflow module can be used for this purpose -- this page has a good overview.
Also you might take a look at these modules, one of which might work well for you:
You don't need contrib modules for this. You can edit the content type and set it to be unpublished by default. Only users with the administer nodes permission will be able to mark it as published.
There are a couple of modules that also split out publishing permission from administer nodes, in case you want to allow someone the right to publish without granting them full administer nodes perms.