Know how light mixes with the trees around your property. You may think you've got the perfect spot for a solar panel, but watch it throughout the day. The sun coming in from different angles may lead to surprising shadows from trees and foliage. This will affect your solar output.
Experimental set-up of an active cooling installed in a 20kW PV park. See results here: https://sciencedirect.com/science/article/pii/S0306261917316859.
Always use non abrasive cleansers on your solar panels. An abrasive cleaner can scratch the surface of the panel and cause permanent damage and affect how well the solar panel works. There are commercial cleaning solutions to use or you can use a pool skimmer with a very soft cloth on it.