Give many man thine hear, but few thy voice.

Polonius says this to Laertes, as he is preparing to leave. This actually runs parallel to one of the rules I have learned. People like you if you listen to them, but a lot of the time they really don't care what you think. So, if you want people to like you listen to them, but don't talk excessively.
I think Polonius is also trying to tell laertes not to give his good opinion out to cheaply. I used to think that I had to tell my opinion all the time, and argue with everyone. Then, people started to treat everything I said as an argument, and I realized my mistake. Sometimes I just need to keep quiet!