So far my tips and tricks are these: plan ahead, pack only cameras that can be replaced, have a waterproof or water-resistant camera bag AND a coat (So you can dig around in your bag with the coat over the opening to avoid letting the rain in), and don't stray too far from your car. Also, have a couple of towels waiting for you your car, just in case.
Most of my rainy day photography has been done in spittle type rain, but I have taken a few shots in certifiable rainstorms--mostly under the cover of something. By "cover" I mean things like my car, a bridge, a porch, or my coat pulled up and over my camera as best as I can.
Then there are a few cameras that I might make an exception for, ones where I just pull them out and quickly get my shot and then stuff the camera back in the bag. My Polaroid Spectra and Polaroid One cameras get that kind of treatment because I can frame the shot, take the picture, and hide the camera away really quickly. And those cameras didn't cost me an arm and a leg, so I am a little more brutal with them.
Sunny days in Zion National Park:
Stormy/rainy days in Zion:
As you may have guessed, the weather has been stormy around here for the last couple of days. I'm planning on going out to enjoy it tomorrow.