What I do when I get stuck on a puzzle is to put it aside for a while and then go back to it with a fresh view. On a really difficult puzzle, I might do that several times. It frequently works for me. They also get easier for me once I figure out the puzzle's theme.
Once I get to the point of being really stumped on a clue or two, I'm not above doing some research to find an answer. That helps me to learn new things and it might just provide stimulus for other answers to come to me. And, since it's not a competitive activity, I don't think of it as cheating, but rather as learning. Just my take.