10 Essentials

Back in, I think the 1930s, some group in Seattle came up with a little list of what you should bring on a hike. I learned about it when I was in Girl Scouts, and I still usually carry these on my hikes.
"Be Prepared" is not just for Boy Scouts.

(shamelessly copied from REI)

1. Map
2. Compass
3. Sunglasses and sunscreen
4. Extra clothing
5. Headlamp/flashlight
6. First-aid supplies
7. Firestarter
8. Matches
9. Knife
10. Extra food

An example:

No sunscreen in this foggy winter's day assemblage.

I had my map in my pocket for this picture, so just imagine that next to the compass.

From L to R, top to bottom.
Baggie of nuts and raisins, compass, insulating emergency blanket, water bottle.
Small light (in round tin w/ spare battery), chapstick and whistle under that, hank of line to the right, pocket knife, firestarter, hand sanitizer, first aid kit in two plastic boxes, ACE wrap.
Lightweight gloves and a wool hat, a wool shirt.
Rain pants and a rain coat.

It all fits in an old fanny pack I have (the rain coat is strapped to the bottom of the pack).

Sometimes I put matches or a BIC lighter in there.
Sometimes I have more and warmer clothes.
Sometimes I leave the rain gear at home.
Sometimes the first aid kit is larger or smaller.
Sometimes I have more or less food.
Often I add a little bit of toilet paper and a ziplock baggie for trash.
On a hot summer's day I have two water bottles (there are water purification tablets in my first aid kit.)
My regular glasses are photogray so I skip the sunglasses but almost always take a wide-brim hat.

Some random comments on my gear:
My headlight is in a tin since the switch is easy to push if it is loose in a pocket. It also gives me an easy way to carry a spare battery and the tin makes for an easily identifiable shape if it is necessary to find it by groping about.

I would normally carry a poncho-tarp instead of the rain jacket, but the poncho has disappeared out of my gear closet (or fell down behind, or I put it in a 'safe place') so when it reappears I'll swap out the rain jacket. I like having the ability to make a little shelter to get out of the rain or the wind or the sun.

The hank of rope is useful for shelter-making as well. I have also repaired my shoe with it (there is a sewing needle and a bit of thread in my first aid kit).

When I get a post about my first aid kit together, I'll link it here.
For now I'll say that hard-sided first aid kits may be more difficult to pack, but they prevent the sharp things from impaling the squishy things and the squishy things from leaking all over everything else. Nothing like having a thin layer of neosporin all over the rest of your first aid kit.