Standard acrylics like our 3/16" and 1/4" thick PMMA really show the fingerprints! However, our default acrylic styrene material has a non-glare surface that really hides fingerprints well. Occasionally, though, you might get other debris on it and want to clean it.
Your keyguard should only be cleaned with a mild detergent and warm water. Don't use hot water, because you might warp the acrylic. NEVER use a strong cleaner that does not state it is safe to use on acrylic or Plexiglass. Novus #1 is a good product to use for cleaning, as is soft soap. Glass cleaners are generally OK, but don't use it if it contains a strong alcohol. We like lens cleaner for fingerprints and light smudges. For heavier cleaning, we use Odoban® Real Citrus spray.
Keyguards do get scratched, though the non-glare acrylic styrene hides them well. You can polish out light scratches with car wax or a plastic polish like Novus #2. For heavy scratches, use a polishing compound like Novus #3 or Turtle Wax Rubbing Compound. Warning: If you use one of those latter compounds, you may have a tough time restoring the high shine with the plastic polish. It will take some effort on your part.
Suction tape won't stick well if it gets dirty, however, it can be restored with a mild detergent and warm water. Use a lint-free cloth to squeeze out the water as much as you can, then let it fully evaporate before re-attaching it to the screen. If you get it clean and dry, it will stick like new again.
Finally, be aware of how your keyguards are handled. They will take a lot of impact without cracking, but can be cracked if they are bent too far. 3/16" and 1/4" PMMA is quite brittle, and though harder to bend than the thinner acrylics, they will definitely snap if bent, so stuffing them in a back pack or setting them on the floor is not a good idea. Acrylic styrene is much more flexible and won't crack unless really abused. That's why it comes with a 2-year warranty. Actually, it will turn white from the stress before it cracks, so we can always tell when it's been mistreated.
Treat your keyguards well, and they will reward you with years of service!