Most of my jewelry designs have a patina on them. I just like the warm earthy look of a piece after it has been oxidized. I use liver of sulfur, and boy does it stink. I found a tutorial on how to add a Sapphire Patina to a piece of jewelry on a lovely blog called "Melinda Orr Designs". The earrings in the tutorial have a gorgeous blue colored patina. They are really pretty. But just like when using LOS, you will need to be in a well ventilated area, because you will be using household ammonia.
I haven't tried this technique out yet, but it sounds like it would be fairly simple, and you probably already have everything that you need.
Fine steel wool or scotch-brite
Ammonia - household
Plastic container with lid
2 small round flat stones
And of course whatever piece that you want to try this technique on.
Do you have a technique that you use, to get a nice patina that you would like to share?