Lifting weights should be simple: crank through your routine while staying out of everyone else's way, then pick up after yourself once you're done. Unfortunately, not everyone cares to follow the rules, from the blatant ones that adorn every weight room sign to the more subtle pieces of gym courtesy.
Don't get us wrong: dragging yourself to the gym in the first place deserves props, and no one is going to get in your face if you unknowingly make a minor breach in gym etiquette. For the most part, people are only ever focused on their own workout, not what anyone else is doing.
But there are a few points you'd be wise to pay attention to, since repeat offenses could earn you some not-so-kind looks from the other gymgoers.
Easy with the grunting
Nothing wrong with some heavy breathing or a quiet grunt here or there. But when you become one of those guys who's practically shouting during each rep, it's a bit much. You may be tough, but you're not that tough.
So unless you're going for an insane one-rep max, don't get too loud.
Grab your dumbbells and step away from the rack
Doing your shrugs, curls, raises, or anything else directly in front of the dumbbell rack prevents anyone else from accessing the weights in front of you. A good rule of thumb is to back off at least five feet.
Let your fellow gym-goer work in with your sets
If other people need to use the same equipment at the same time as you, let them. Do a set, rest while letting someone else do theirs, and repeat. It's a minor annoyance, sure, to change the pace of your set to sync up with another person's, but sharing is a skill that anyone should be capable of.
Don't ask to work in with someone outside of your weight class
Having said the point above, there is a bit of a caveat. Asking someone to work in, like if they've been on the squat rack for 30 minutes and you really can't wait any longer to do your own set, is totally fine if you're using the same weights.
What's not ideal is asking to work in with someone if there are three plates and change on the bar and you can only lift one. You'll waste the other person's time by re-adjusting the weights each set, or worse, by making them do it.
An easier solution: just ask the person how many sets they have left. They'll get the hint that you've got dibs on using the equipment next, and that they should move it along so as not to delay you.
Don't monopolize equipment you aren't using for its intended purpose
Curling in a squat rack is maybe forgivable if the gym is nearly empty and no one else is asking to use it. What's not cool, though, is when somebody's waiting to put the equipment to good use while you're flexing your biceps in the mirror with an exercise you could be doing elsewhere.
We all have to start somewhere, and if it's an honest mistake, no sweat. But if you've been going to the gym for a while, and you're doing push-ups in a power cage despite knowing that it could be put to much better use, that's not cool.
Don't reserve equipment you're not using
Don't lay your towel down to reserve a bench, then disappear to chat or check your e-mail. Only set up when you're ready to get down to business.
Keep your bodily fluids in check
This one should go without saying. No spitting in the water fountain, relieving yourself in the shower, or leaving sweat all over the equipment.
Clear your weights. Always.
Leftover weight on barbells is the scourge of most weight rooms. If you got them on there, you can get them off.
Re-rack your dumbbells
No one should have to spend ten minutes searching for a set of dumbbells that were left hidden in the corner of the gym. Finish your set and put the dumbbells back in their rightful place on the rack.
Follow those and not only will you have a more efficient workout, but you'll get along just fine with all your fellow lifters.