Completing Album Artwork?

Following success with iTunes Match wish to now ensure all libraries have the correct Artwork - how is this best achieved?

Looking at the behaviour of iTunes (reported in https://discussions.apple.com/thread/3650114?tstart=0) it seems wise to ask this more general community for help since ensuring correct Album Artwork must be a very common theme with a solution not necessarily associated with iTunes Match.

Many thanks in anticipation, all advice gratefully received.