Nice points. I'd also add;

Spend time thinking about it. It's something that seems obvious, but I know I pass over it more than I should. Since answers seem to come unconsciously it's tempting to just wait for a solution to arise and to go think about other things. Unless you keep the problem in your head during down-time, before going to bed, in the shower, taking a walk etc... then you won't be processing for an answer. It's tricky to coax subconscious thoughts to answer the questions you want, but continual conscious thought on the topic is the most straight forward approach in my experience. If you're thinking about other things, you won't get an answer.