It sounds like you understand the principals quite well, so no longer need to memorize rules. It is all about light, so look for interesting light. It occurs at all times of day. A couple "rules" which may be helpful, though: a) The bright, fluffy snow on the branches all falls off after about 10:00am, (usually down the back of the photographer's neck). b) In most places (in the U.S. anyway), mosquitoes the size of hummingbirds come out in the evening. [Donald, the Pacific Northwest always astounds me in their absence. ]