Shane - I'll add that if you know a piece has been used to melt lead - do not use it for cooking. Beyond that, it's pretty much like Tom says.
There are small heavy pots out there that do have a history of being lead pots and are often confused with cookware. As far as 'cookware' goes, I've never run across one that I was suspect of, per say, but I've turned my back on many that just were too far gone to think I could restore them. There's plenty of good cast iron out and about. Unless it's something special I walk away.
~chuck