Gym Etiquette:
Know the rules at your gym. Every gym has a different set of rules its a good idea to get to know them just so there is no confusion. Example: Does your gym allow chalk?
Don't drop or throw weights. Dropping wights is dangerous for anyone in the area. Not mention it also ruins the weight itself (especially dumbbells). The floor also suffers damage.
Wipe down the equipment that you just used. Especially if you're sweating up a storm. Who want to get on a sweaty piece of equipment, especially if its not your own sweat!
Put equipment and weights away when you're done with them. If nobody put there stuff away the gym becomes impossible to workout in.
Wear clean clothes. Nobody wants to smell your 3 day in a row clothing.
Before you use a piece of equipment check to see if anybody is already using it. Sometimes a person using a piece of equipment will go get a drink or they are going to get some dumbbells to work on that bench.
Sharing equipment: Sometimes you can find yourself in a situation where the piece of equipment that you need is being used by someone else. First thing you can do is ask how many sets they have left. If its a lot either look for an alternative piece of equipment or ask if you can work in. If you do work in make sure you put the equipment back to the way they had it before your set.
Saving Equipment: There are times when you need to leave your piece of equipment to either get some weights or get a drink. When this happens simply put your towel or belt on the bench as a reserve. Don't take too long.
Step away from the dumbbell rack when not using them. Other people need to get to that rack to get their dumbbells and if you're standing there they can't get to there dumbbells.
Don't stand in front of the mirror in front of someone else. A lot of people use the mirror to check their form or see what they are doing don't stand in front of them.
Don't get too close to someone lifting. For safety sake keep an appropriate distance away from the lifter. For your sake and theirs.
Give people their mental space when lifting. Different people have different styles of lifting weights some people need to keep focused before a big lift or during an intense training session. Don't go up and just start talking to people in the middle of lifting.
No screaming or swearing. Sometimes when lifting intensely you need to give out a grunt but there is no need to scream out a the top of your lungs. Thats more for attention than assisting your lift.
Limit cell phone use. Nothing more annoying than having to listen in to someone else phone conversation while you trying to lift. Scrolling through Instagram or Facebook while sitting on the bench someone wants to use is not cool.
Concentrate on your Workout, Not What Others Are Doing: People don't want you to give them advice unless they ask for it. Unless you see someone doing something that can make them hurt themselves focus on yourself.
Dress Appropriately: A gym isn't a fashion show and if you don't dress appropriately it distracts everyone else.
Obey cardio equipment time limits. Most cardio equipment has time limits usually 20 minutes, this is to insure everybody gets to use the machine.
Bottom Line:
Remember to treat others as you would like to be treated. Act like the equipment in the gym is yours and you will treat it properly not destructively. and always remember a gym can be a dangerous place so be aware of you surroundings