Here are some tips from a TV editor in Hollywood. I changed a few words around since it came off another site. A lot has to do with how long to hold on a shot. There's this tendency to love your shots so much that you let them play out too long like a Phil Bloom moving postcard. Don't do that.

-Most shots are between 2 and 4 seconds long.

-Shots that are less then two seconds and especially less than 1 second are usually decisions driven by the music, and you're probably cutting right on the beat.

-Shots that last beyond eight seconds are either incredibly dynamic, or are a restricted POV shot (like a surveillance cam or similar) that get their power from being a restricted POV.

-The longest I can remember holding a shot was 42 seconds--it was from the helmet-cam of a cop chasing a drug dealer through fenced-in backyards.

-My shows have wall-to-wall music (too much, I think). A cue usually lasts around twenty-five seconds. Ten seconds happens. The only times I let a cue get much beyond 30 seconds is if has some big-time change-ups in it, so its essentially a different cut.

-Most scenes are between two and four minutes, but there's a lot of wiggle room in this. Having said that, it's rare for a scene to be less than forty-five seconds -- once it gets less than that, it usually becomes part of a montage with just a sound-up or two.

-I try to keep talking head scenes down to 75 seconds.

-When I'm cutting static shots (like an establishing shot), and there's no music or rhythmic sound in the cut yet, I find myself counting a four-beat in my head--probably lasts three seconds. But it's also worth noting that the length of these shots will almost immediately succumb to rhythm of whatever sound is put in there.