Repository is one of the fondamental maven concept. It's simple to understand but fair usage request a bit of practise.

You should have a clearer idea of repository management best practises through the following examples and #counterexamples.

Initial configuration

This configuration come with maven without doing anything.

The "simple project" pom. 

Extended usage

Without repository manager 

Take a look on the "extended project" pom.

With repository manager

The "extended project" pom don't change, we just add mirrors section in the settings.xml (M2_HOME/conf/settings.xml or ~/.m2/settings.xml).
Take a look on the Mirrors definitions in settings.xml. 
 

Complex usage

Counterexamples

Single repo mirroring multiple repositories

THIS IS A COUNTEREXAMPLE

Mirror repository defined in place of original repository.

THIS IS A COUNTEREXAMPLE

Annexes

pom.xml

Simple project

Extended project

  Note that some repository declarations are useless:

• Jetty is now available on central repository so you can remove

• Project only need snapshot version of cargo plugin so you can remove

•  The project don't have any dependencies on snapshot version of codehaus artefacts so you can remove

 Advanced project

Settings.xml including repository mirrors definitions