Stained glass looks its best when its taken care of, and loved. The methods I use in my own art I display in my house are below to help you keep your glass pieces in their best form.
All my solder contains lead unless specifally mentioned that its lead free, it is highly recommended that you wash your hands after handling any stained glass pieces.
For the best results, only use soft non abrasive cloth, like microfiber, for polishing your glass art. Most pieces will shine back up just a simple hand polish with a microfiber cloth. If your piece needs a little more love, you can use dishsoap to wash your piece; do not use the same cloth you would wash your dishes with (you know the whole lead thing). You can dry it with a paper towel, then add a simple car wax to shine it back up. For black and copper patina pieces, that patina will naturally tarnish over time, copper more so, to a brassy finish. You can revive the brighter copper color by doing a car wax polish up.