Never use an abrasive material to clean your solar panels. Doing so could cause them to become scratched and less useful than they were when they were installed. Your best bet is to have a gentle cleanser and cloth on hand to clean your panels so that you know that you have what you need when the time comes.
Keep your solar panels out of the shade. It might seem obvious, but your solar panels do need sun. Make sure that you are not installing them in the shade. Trim back the branches on surrounding trees if you need to. Failing to do so could cost you more than half your energy output.
High temps from the sun on a cold day.
You don't necessarily have to stick the solar panels in the typical locations you see in the brochures. There only needs to be a small gap of approximately 1" behind the panel for air circulation. You can find interesting positions anywhere on your property that work with the style and design of the surrounding area.