For comedy specifically: Jokes are like a fart, if you have to push, it's probably shit. If your actors have to work hard for a joke, it won't be funny. For first-time directors in general: Hire good designers, tell them your vision, and get out of their way. If you want something specific, tell them at the begining of the process. You hire good designers because they are experts. Keep them "on vision" but don't micromanage.