I usually steam broccoli for about 8-10 minutes because I like it soft. If you think 3 minutes is enough, just pull a piece out and try it. If it's too crunchy let it go longer. I really love the flavor of broccoli, so to season I just put butter, salt, and pepper on it.
I steam cabbage, but I usually do it with smoked sausage to flavor it. It's a great way to make a whole meal in the steamer, plus you get rid of some of the fat from the sausage. Like the broccoli, I just use butter, salt, and pepper on the cabbage. Oh, and I usually steam the cabbage about 20 minutes, or until I can put a fork through it relatively easily...