My first mushroom lesson: Never, ever let mushrooms touch water.
Back in college, my roommate and I worked as "mother's helpers" every now and then for a posh local family. Once, when helping them with some party preparations, we were told to clean and slice mushrooms (I think they were white buttons) and we did something that was apparently unthinkable and unforgivable.
We rinsed the mushrooms. In the sink. With water.
We were swiftly schooled in "proper" mushroom cleaning protocol: rub each one individually with a clean paper towel. From that day, I either secretly and shamefully rinsed my mushrooms, or just avoided them.
My mushroom redemption: Rinsing mushrooms is not a sin.
Years later came my culinary school externship and I was once again instructed to clean and trim large quantities of mushrooms, this time fancier varieties like morels, maitake, shiitake, and porcini. Before I could dutifully gather a mountain of paper towels, I got my second lesson in mushroom care.
If the mushrooms aren't dirty, don't wash them. If they have a little debris on them, wipe them. If they are very dirty, have a lot of hard-to-reach debris, or little critters living in them, rinse them, but never soak them. Dry them well and cook them soon after.
I liked this second lesson much more than the first. Ever since, I've stuck to what I learned then, and the texture or flavor of my mushrooms has not suffered. More importantly, I no longer suffer from mushroom-washing guilt. And you don't need to either—this is where the slideshow comes in.