*If there's one thing to remember, do not scratch or collide the lenses with the stage clip that holds the slide in place.*
*Pro tip: You have more fine tune control of the focus knob if you turn it with your arm rather than with your fingers.*
Q-tips! Yeah, just take a Q-tip and clean off both sides of the lenses. If your image looks washed out, the natural oils on your hands might be the culprit. You'll be surprised how much of a difference it can make! Besides that, sometimes dust and debris can get on there too.
The other places that might get dirty is the outside and inside surface of the acrylic stage. The outside is pretty straightforward, and to access the inside surface just remove the LED light and use a Q-tip to clean off that side.