Keep Feet Planted, Back Flat
Keep your feet planted firmly on the ground and your back flat on the bench. Do not arch your lower back as this compromises your spine and can place additional stress on your neck. A significant injury could keep you out of the gym for a couple of weeks.
Get A Spotter
When lifting heavy weights, get a spotter to assist you. Even if you have to ask a fellow gym-goer it is more important to ensure proper form and safety rather than risk injury.
Use Good Posture
Use good posture while exercising on cardio equipment like the treadmill, bike or stair climber ... bad posture on workout equipment can cause back and neck pain. To address this, do NOT use the rails unless you need them for balance. Keep your posture straight and relaxed with your core tight and your eyes looking straight ahead.