Rinsing mushrooms is actually a matter in controversy -- silly that people take this stuff so seriously, isn't it?
Mushrooms can be very absorbent and shouldn't be soaked before sauteing. On the other hand, if you're going to toss them into something that's already wet, likie a broth, it doesn't matter at all. If you've ever reconstituted dry mushrooms, you know the whole "don't get mushrooms wet" thing can be a little overblown.
Many good cooks rinse mushrooms quickly with the sink spritzer. Some don't. Some species are more absrobent than others. The regular white mushrooms, criminis (baby 'bellas), portabellas, and cepes are probably the most absorbent of all -- which figures because they're the most commonly avaailable. Although they're grown in a "sterile medium," I usually spritz and dry because of the particular nature of that medium. But if you decide to just brush them off with a soft brush, you're in very good company.
Now moving along to the next step -- if that happens to be sauteing. Your mushrooms should be dry. Your pan should be hot before you add any oil or fat to it.
Whoops! You wanted wow! tips. Always preheat your pan before adding oil. Always heat the oil before adding any food.
For mushrooms (as well as almost all sautees) that means a medium high flame, and just enough oil to fully coat the bottom of the pan.
Now add the mushrooms. Don't disturb them, don't stir them, don't put salt on them. Do one thing: Wait. The idea is to brown at least one side of the mushrooms before turning them -- agitating them will cause them to give up their moisture which will prevent them browning. After a minute or two, you'll start to smell them cooking.
Shake the pan and the mushrooms won't move much -- they'll stick to the bottom of the pan. Why? Because there's a chemical reaction occurring on the surface of the mushroom where it gets the heat from the pan that creates a kind of glue effect. When the reaction is complete, the mushrooms will release. That means that after another minute or two, when you shake the pan again, the mushrooms will move of their own accord. Now you can flip them, season them, add a few or some shallots; and when the second side has browned, you can add whatever else it is you choose to add.
Now take a mental step back and think about it. 92.7% of the people who made such a big deal out of not washing the mushrooms didn't cook them properly and caused them to give up moisture they ended up cooking in. Self defeating, n'est ce pas? But that's how it is. There are a lot of ways to mess up.
Here's another "wow," techinque, perhaps the biggest "wow" of all. It applies to salt and pepper, and to most other spices. It's called "tasting." Always start by underseasoning, then taste and adjust. Try and add your salt and pepper at several times through the course of cooking. This is called "layering flavors," and it's a big part of modern cooking.
If I could choose one techinical tip -- heck! I guess I did -- the one piece of "expert advice" that makes the most difference: it's frequent tasting to get seasoning levels, especially salt, perfect. More than anything else, that's what separates good cooking from average or bad. Even at the restaurant level.
Probably, the second most important and least understood set of techniques is learning to use a hot pan properly -- including knowing when and how to turn food. The mushroom example is just one -- and unfortunately it's a little bit specific. Most foods aren't quite that sensitive. But ... hot pan, cold oil. Then hot pan, hot oil, add food. Then, turn food when it's ready to be turned and not before. Those things are gold.
Cooking is a journey of discovery. At some point it all starts to make sense -- flavor combinations for instance. I know it all seems very complicated, like there are a million discrete, unrelated things to know. But, the more you learn, the better able you'll be to fit all the new information into some sort of organized gestalt. Trust me on this.