How do I choose the right fitting for my lampshade?

If your lamp came with a harp, you'll need a SPIDER fitting. The harp will look similar to this: 

If your lamp did not come with a harp, you'll need a EURO fitting. The lamp base will look similar to this: 

If you'd like to hang your drum shade as a pendant, you'll need the EURO fitting. It will connect like this: