The Essentials:
Day pack
Trekking poles (optional, but recommended)
Map
Compass
GPS
Knife
Water bottle and/or bladder
Water filter or purifier
First-aid kit
Lighter
Headlamp
Toilet paper or portable bidet
Food:
Lunch and an extra day’s supply of food
Trail snacks
Additional:
ID
Cell phone
Credit card and/or cash
Sunscreen and SPF lip balm
Sunglasses
Sun hat
Hand sanitizer
Bug repellent (avoid repellent that has DEET listed as an ingredient, as it can ruin gear)