No rolling light dumbbells across the floor. I can somewhat accept guys rolling heavy dumbbells back to the racks after a set, but I have seen guys roll 50s across the floor even before they lifted them!

No dropping dumbbells unless they are too heavy for you to crontrol all the way to the ground. The same guy who rolls the 50s across the floor also drops them to the ground like they were 150 pound dumbbells.

No circuit training. The only time this would be acceptable would be when the gym was totally empty. But there are one or two guys in my gym that try to run a circuit routine when the gym is the most packed.

Tell people when they are doing something wrong. I'm not an expert on weight trainning but once and a while I will see someone doing a lift totally incorrectly and I will let them now. I do it politely, but still some people get upset. I think if more people did this people wouldn't get so upset when it happens.

When you ask someone for a spot, be ready to lift. This guy asked me for a spot the other day and then sat there for about a minute getting himself psyched up for it, I guess. He was just wasting my time.