Every trip is different, so every list will be different.
I use the "10 essentials" to determine what to bring on a given trip. This particular version of the 10 essentials is a "systems" approach, not a 10 item check list.
Navigation
Paper Map and Compass, GPS, etc
Illumination
Sufficient lighting for navigating at night (headlamp, possible spare)
Sun protection
Sunblock, sunglasses, hat, Buff
First aid
Containing things you think are important in back country (+ bug repellant?)
Repair Kit
Things you need to fix your gear. E.g. extra shoelaces, spare batteries, knifes, wire, patch for your air mattress, etc.
Fire
2-3 ways to start a fire. Stove if you need one.
Shelter
Can be as complicated as a tent, or as simple as a tarp. I also think about sleeping bags, air mattresses, etc in this category
Extra food
Food to stay an extra 24 hours beyond expected trip/day trip
Hydration
Water, a way to carry it, and a way to make more
Insulation
Extra layers to deal with rain, cold, or an emergency overnight
I add an 11th essential which would be communication. This is where your PLB/Locator device like an in-reach goes, as well as 2 way radios (if used), a cell phone (if used).
By doing a quick review of this list, I am assured that all bases are covered. A day hike would see a much smaller set of gear in my pack when compared to an overnight where I might have 20lbs of basic gear. But each of the 10 (11 actually) essentials are reviewed and addressed.
The key is, how do you cover the list without carrying 100 lbs of gear on a day hike! Mastering this takes experience...