Clean Gym Equipment
It seems like common sense, but not everyone is aware of 'gym etiquette'. Grab a clean towel and take it along as you move from one machine or piece of equipment to the next. Wipe down where you touched the equipment, even if you don't feel 'sweaty'. Gym equipment can be covered in bacteria from multiple people using it all day long. The kind thing to do is make sure you wipe it down with a towel, or better yet, an antibacterial wipe (many gyms offer these near the machines and weights). You'll feel better and so will the other folks around you!
I go to the gym daily and it's such an easy thing to do....when you finish with your equipment just wipe it down for the next wanting to use it. Sure makes me smile when I know the person in front of me took care of it as I would.