Most of it is just looking to see patterns and differences. Once you start looking, a lot of it is very clear; sometimes you can clearly see a line that's different from the rest of the surface of the water, moving toward you. Or you can see a demarcation where the water looks darker in one area than another. Or a place where the reflections of light on the water suddenly stops. I highly recommend going out to a body of water and just spending some time really looking at it!