What's the best way to clean copper pots and pans?

I use salt and lemon juice...It does a very good job..

I use salt and scrub with a sponge. The abrasive salt will clean the copper.

The folks at Williams & Sonoma have told me to use a thin paste of Bar Keepers Friend

My favorite polish for all metals from silver to brass to copper is a cream called Maas. You can find it online. I swear by it. I ahve restored a lot of badly tarnished pieces with it. For a simple homemade solution salt and vinegar in combination are a good copper cleaner.