Honestly, I have the best success adding cold-brewed ready-made coffee that you can buy at the store (the kind you mix with water or milk to make coffee). Just add to taste before bottling and it works wonderfully.
I always find that grating ginger works best (better than cubing), and a few ounces with about 10mins left is nice, but adding it to the secondary gives is a really nice aroma and a little kick.