I have 3 repositories in my settings.xml because I need artifacts from all of them. Whenever a dependency is not found, Maven tries
Downloading: http://some.
As far as I know, the order of the repositories in your pom.xml will also decide the order of the repository access.
As for configuring repositories in settings.xml, I've read that the order of repositories is interestingly enough the inverse order of how the repositories will be accessed.
Here a post where someone explains this curiosity:
http://community.jboss.org/message/576851