1. Re-Rack Your Weights
This is the #1 rule. If you can lift it, you can put it back. Leaving weights on the floor is a safety hazard and disrespectful.
2. Wipe Down Equipment
Nobody wants your sweat. Use the spray bottle. Fitblues "Rest Timer" is a great time to clean up.
3. Don't Curl in the Squat Rack
Squat racks are for squats (and overhead press). Curls can be done anywhere. Be mindful of equipment scarcity.
4. Headphones ON = Do Not Disturb
If someone has headphones on and is focused, don't try to chat. If you need to ask "Are you using this?", catch their eye and make a gesture.
5. Personal Space
Don't stand 2 inches from someone while they are lifting heavy. It's dangerous and distracting.
Conclusion
Respect the space, respect the people. The gym is a shared sanctuary.