Known for it's soft, supple texture, suede's unique finish puts it in a category of its own. But that signature texture also makes for tricky care. It's not difficult to maintain, you simply need to know what works best.
Because of suede's matte finish, it can be easily susceptible to stains and thus, people often want to treat it with some sort of protector. Yes, you can use a spray like Collonil's Waterstop, but those treatments often minimize the flexibility, change the suede's color and make it less breathable. A wise and stylish man once remarked "If there was an effective treatment to protect suede, wouldn't manufacturers be using it?" You're probably better off not treating your suede and simply avoiding rainy days.
You can't polish away scuff marks or stains. You'll need a suede eraser (basically a brick of crumbly rubber) to rub away small blemishes, water spots or shiny marks. Rub the stain like you're sanding a piece of wood, until the stain disappears. Then use a suede brush to restore the nap, or fuzzy texture of the leather.
For extremely dirty shoes or those that have large stains from salt or getting wet, you'll want to clean the whole shoe. Wet the entire outside of the shoe by applying a light coat of water with a small brush or cloth. Use a sponge or dry cloth to soak up any excess water, and then let the shoes dry at least overnight. Be sure to insert a shoe tree while it dries to prevent shrinkage or a lose of form. Once dry, go over them lightly with a suede brush, making sure to move in small, circular movements to keep the nap even. You may want a more detailed suede brush that easily gets into shoe crevices.
If there aren't large stains, but you want to freshen up the leather, try steam. Hold the material about six inches above the steam (from an iron or steamer). Once the nap becomes heated you can brush it up with a suede brush. Using short strokes from one direction (don't go back and forth), you will help restore the softness and remove some of the surface dirt and dust that would ultimately discolor the shoe.