Sherry, you brought up a great topic: Gym Etiquette, I though I would add some things that people may find humorous.
1) Share equipment: You are not a five year old. Nothing in the gym is "yours". Let people work in. Even if they don't want to work it, don't feel like you have to invoke your "Squatter's rights" on a piece of equipment.
2) Leave stuff how you left it. Rerack weights and wipe stuff down. Also, disinfectant does not work drowning. More is not better, it just become toxic.
3) It is OK to be friendly or even start a conversation, but don't destroy the funk of someone's workout. That includes offering advice and hitting on someone. It is perfectly Emily Post to say "Hey, I am trying to work out." to any unwanted conversation or advances. Personal note: I can't imagine a worse place to hit on women then the gym. They see you at your worst, you can't avoid them, and I am sure they don't want to be the object of locker talk. Just saying.
4) Spots: If someone asks for a spot, give it to them unconditionally, unless you don't mind others thinking you are a self-absorbed dickhead). If you get a spot, you are on the spotters schedule, not yours, they are trying to workout to. Offer spots, it makes you look friendly. If you get pinned, it is your own fault. Don't complain about a spotter grabbing the bar too quick, they are not a professional.
5) Typically the guys and gals in better shape are usually the ones that also understand gym etiquette the best UNLESS their t-levels are so out of whack. No reason to be intimidated, there is no caste system in the gym. Also, unlike what other people think, they are also the most knowledgeable in a practical sense. If someone has a lot of book knowledge, but does not look or perform the part, the knowledge is used to create excuses. I think Planet Fitness paints a very judgmental and prejudiced view of this. I would post a PF video, but I don't want to give those douchehats free advertising.
6) Perspective: It is a workout, not the Olympics. No need to get all "Type A", obsessive-compulsive, or be a control freak about your workout. Act like a human in a society. Personal note: There is always one person in the gym who gets there at the same time everyday (typically mornings) and has to use the same treadmill every time. If you see that person, avoid them, they are really annoying and generally pretty useless socially as well.
7) Showering: Don't talk to anyone while you are naked. No one will say anything, but they are uncomfortable, annoyed, or very likely, BOTH.
8) If you don't want people to look at you, don't dress in a way that makes people look at you.
9) DON'T CURL IN THE SQUAT RACK!