What should I look for in a good arthritis cream?

Personal choice. Most arthritis creams work on the idea of a "pain gate, " in which the cream causes a tingle or mild burning sensation that prevents the nerves from carrying pain information because they are already full of tingle/burn information. One common active ingredient is capsaicin. It is important to remember that these creams may dull pain, but they do not fix the underlying problem.
Arthritis. Try any to see which works best for your body. But if you have arthritis, maybe you should ask your doctor for alternative treatments.