Don't plug someone else's leak.

Don't be the good Samaritan trying to help the fish that is giving us his money. I see it at least twice a day at micro stakes.

Help people on the forums or something not the guy that keeps getting stacked and rebuying at your table.

I don't know if it happens at higher stakes, but I see it a ton.

I also see people gloat when they take someone's money. Many times the guy who lost ends up leaving because of this. My wife is happy to give away money at 1 cent 2 cent. She is playing for entertainment which many people do. If you are an ass to her she will most likely take her money and give it to a different table. This goes for when someone sucks out on you as well. She may get a bad beat on someone but if everyone would just stfu she would gladly donk it all right back to the table.