Find an analog from your life to the purpose in the scene. Take it in, feel it in your body, in your breath, in your muscles. Humor is finding ironies, having the ability to release tension in the scene. In the most serious moments, humor can release the tension and allow us to feel deeply. When in doubt, go opposite.
Consistency is boring.
You're never really doing the same thing twice, so each run of scene offers ample opportunity to find something new. There are two keys to keeping discovery alive in a scene. First, you can't judge. You need to allow an insight the time that it needs to take it in and mull over it. Second, you'll only find new things when you're focus is in good working order.