Spray, spray, spray! For suede and nubuck it is especially important that you use a leather protectant as the grain in suede is open and more susceptible to stains.
Investing in a suede brush and eraser is the best was to deal with stains and dirt on your suede products.
If your suede gets wet, let it dry naturally, if there is a little spot, dab it with a dry cloth. For wet shoes, stuff them with paper to their natural shape (not any bigger) and let them dry, away from a heat source. The next day, give them a good brushing to bring back the nap.
You can spray your suede up to once a week with a leather protector to keep away the stains and help them stay water-repellant!