There are many ways to clean a plane and many different products; you can use them or none at all depending on what you have at hand and what you have in mind. If your plane needs a deep, exhaustive cleaning, you may want to use some of those products, but some water, fuel and kerosene might do as well.
Firstly take out all the dust, mud, snow, etc. out of the surface with a cloth or fabric that leaves no residue. If there is snow or ice all over the plane, make sure that you remove all of it before flying.
Sometimes the means or the situation may not be ideal, but even the intentio of lceaning constitutes a good habit.
Windows and windshields should be cleaned with special products in order to avoid scratching it; if you don't clean them properly you will leave marks, they will become opaque and in the end the bill for replacing them will be horrible. On the other hand, never use anything on the propeller except for a cloth moist with water or avgas; any other kind of product might accelerate cracking.
In order to take out stains of any kind, oil drops, etc. the best thing is kerosene, Use a damp cloth with kerosene instead of detergent that dry the aircraft's skin out. You could use regular shampoo as well.
The devil is in the details, and you will see that after you take off.
Cleaning a slam airplane in this way takes about fifteen minutes; it is not a complicated task that doesn't require anything except for a bucket, some cloth and a ladder if your plane has a high or parasol wing. Of course, make sure that you read your operations annual before doing anything on your airplane.
And once you finish both the paperwork and the cleaning, you may proceed with the walk-around inspection and other pre-flight procedures.