How To Protect Your Apple Device (And How Not To) - Apple Watch
Note: This is about protecting the hardware of your device from drops, scratches, fumbles, and splashes- not from malware or other software related threats. Regarding that, see this excellent User Tip - Effective defenses against malware and other threats - Apple Community
After getting your Apple device, you'll likely want to jump right in and start using it. However, it's not only prudent, but necessary, to take measures to protect your device. A small amount of "insurance" money spent on a case or other protector can make a big difference if you damage it, as it may save you from much more expensive repairs to the actual device.
How To Protect Your Apple Watch
Your Apple Watch is well protected. Apple does not recommend that you fit a case or screen protector to the device, as they've been engineered to protect themselves. You can best protect your Apple Watch by simply being careful with it when not on your wrist, and ensuring that you're wearing the device properly, as explained in this Apple article.
Apple Watch Series 1 and Apple Watch (1st generation) are splash and water resistant, but submerging them isn't recommended. Apple Watch Series 2 and newer can be used for shallow water activities like swimming in a pool or ocean. However, Apple Watch Series 2 and newer shouldn't be used for scuba diving, water skiing, or other activities involving high-velocity water or submersion below shallow depth. Apple Watch series 7 and newer also offer increased dust and particle protection.
After using Apple Watch, you can clear out any water with Water Lock, which stops the screen from registering taps. It's on automatically during a workout, but you can simply open Control Center, tap Water Lock, then turn the Digital Crown to unlock the screen and clear water from the speaker.
How NOT To Protect Your Apple Watch
As stated earlier, Apple Watch screen protectors and cases aren't considered necessary by Apple, so if you want one, you'll have to find a third-party manufacturer. There's generally no harm in fitting a screen protector, but a case could make Watch less comfortable to wear and potentially less accurate in its measurements.
It's important to not mistake water resistance with water proofing. Apple Watch is not waterproof, nor is it guaranteed to be. Apple Watch Series 2 and newer are rated for 50 meters, but the water seal does deteriorate over time. Liquid damage isn't covered by the limited warranty, and Apple Watch cannot be resealed or have its water resistance checked. Despite this, it is likely that it'll last for quite a long time.
When cleaning Apple Watch or its bands, soaps or cleaners of any kind should not be used. A water-moistened cloth should be quite enough for cleaning Watch. Apple offers these detailed cleaning instructions here.
AppleCare+
AppleCare+ is a relatively cheap way to protect your device from the hazards of everyday life. Costs range from $49 to $149, depending on your model and choice of plan. With AppleCare+, you receive two incidents of accidental damage per year (12 months), subject only to a small deductible- a fraction of the standard costs for repair or replacement. Depending on the model, the deductible is either $69 or $79 for accidental damage. AppleCare+ is a prudent choice for Apple Watch, as your device is bound to be jostled around during its life on your wrist.
Protect your device, and you'll enjoy the peace of mind that comes with it.
How To Protect Your Other Devices
How To Protect Your iPhone - Apple Community
How To Protect Your iPad - Apple Community
How To Protect Your MacBook - Apple Community