As one who dearly loves mushrooms, I have to say that some mushrooms are better than others to be served just as they are. IMHO, morrels should be cooked with something as they have a robust flavor that can be overpowering. But cremini (baby portabellas), and buttlon mushrooms should be sliced and cooked in unclarified butter, with just a touch of salt. Enoki, chanterels, and straw mushrooms are mild in flavor and can be used effectively as an accent to other foods, where a delicate flavor is preffered.
I guess what I'm saying is that you need to familiarize yourself with mushrooms in their various varities before deciding how to cook them. Also, some people love mushrooms one way while others like them another. For instance, my wife and youngest daughter love button mushrooms that have been battered and deep-fried. I find them too soggy and with too little salt to bring out the natural flavor that I so love. And I detest mushrooms that have been soaked in wine. I believe it overpowers the mushroom flavor, and I don't like the wine flavor anyway.
I am a true believer in making things to suit my tastes, and asking everyone else how they like whatever it is that I'm making. I try to tailor the meal to everyone who will be eating it.
But first, become knowledgeable about what you are cooking, and be aware everyone on this site has their own individual preference. So your answers are likely to be many and varied. Choose the one that best suits your taste or needs,
The basic answer is to cook sliced, in some type of fat, with a bit of salt and until they just begin to turn golden, like the people befor me have epxertly stated.
Seeeeeeya; Goodweed of the North