Having the 10+ Essentials items listed below in your backpack is of no value unless you understand how to use them.
Map and Compass
Carry and know how to use a map and compass.
Always carry a detailed printed topographic map of the area you are hiking in, I use the AMC maps printed on waterproof and tear-resistant Tyvek, or you could use a protective case or plastic covering such as a Ziploc bag to protect a paper map.
Always carry a compass. Always.
It’s ok to carry other navigational tools such as an altimeter or GPS receiver or to use the GPS on your phone, BUT.. don’t rely on technology, as all tech is prone to failure when you need it most (Murphys Law).
Whistle & Signaling Device
For summoning help, a whistle will outlast your vocal cords and can be heard for much farther. A signal mirror can be used to reflect sunlight to get the attention of someone searching for you.
Knife &/or Multitool
A knife can be used to cut food, rope, as well as personal protection. It can be used to create kindling for fire starting by creating a feather stick and the back of the blade can be used with a Ferro rod to create a spark to light a fire.
Your most effective options are lotion or spray repellents containing DEET or Picaridin, and/or clothing that has been treated with permethrin (any clothing that is treated MUST be allowed to dry at least 4-6 hours before wearing !).
I prefer the Picaridin as it does not harm the plastics on my camera gear, DEET will permanently damage plastic items that it comes in contact with, including camera gear and sunglasses.
Carry and use sunglasses, sunscreen for the skin and lips (or lip balm), and clothing for sun protection, if you are hiking above treeline or in an area with open sky, wear a long sleeve sweat-wicking shirt and a hat.
Wear non-cotton fast-drying clothing, underwear included, wool socks, moisture-wicking shirts and be prepared for the unexpected, 80 degrees at the trailhead can turn to 40 degrees or lower above treeline especially when there is a wind the 40 degrees can turn into below freezing temps very quickly (there is always wind, even on the lower peaks). The weather in the mountains changes constantly even in the summer months, and if you become injured and need to spend the night you need to have what you need to keep warm and dry as the temperature extremes can be quite significant, including items that can be layered.
Hypothermia can set in quickly if your activity is limited due to injury so always bring extra insulating items, fleece jacket, down or synthetic puffy jacket (they are compressible and don’t weigh hardly anything), hat, mittens or gloves, and raingear and a heat reflective bag or blanket.
Water crossings don’t always go as planned so include extra socks and waterproof boots do you no good when it comes over the top.
Most, if not all, day hikes are planned with the expectation of returning to the car at the trailhead before dark. Don’t count on it.
Always carry two sources of light or more, and extra batteries for all the devices, I carry a LED headlamp and a LED flashlight. It is very hard to read a map in the dark, it is also very hard, if not impossible, to see the trail or trail markers or cairn’s to find your way in the dark, especially under the tree canopy during a rainstorm.
I recommend LED devices instead of incandescent as they are less likely to fail if dropped when on. (the filaments in incandescent bulbs are very fragile and consume far more power than LED)
DO NOT rely on your phone for light, it’s not bright enough, will kill your battery, and will make your phone useless if you need to call for help if injured or lost, assuming you have a signal – there is very limited coverage in the mountains, and when you need coverage there won’t be any.
Carry and know how to use a first-aid kit, that includes knowledge on how to use all the items in your kit.
Do not let a first-aid kit give you a false sense of security.
Be aware of the regulations regarding open fires in the area where you are hiking or camping.
Carry more than one tool to start and sustain an emergency fire.
I carry a butane lighter, a Ferro rod and striker, and waterproof matches in a sealed container as the last resort. I also carry a sharp knife that can be used to shave kindling when no other dry materials can be found.
Know and practice the proper way to start and maintain a fire.
Firestarter aids such as Wetfire tinder tablets, cotton balls dipped in vaseline, or fatwood are indispensable for igniting wet wood quickly to make an emergency campfire. Other common firestarters include candles and crayons.
For shorter trips, enough food for the “planned” hike and a one-day supply of extra food is reasonable.
You should always bring some food that should require no cooking, be easily digestible, and store well for long periods.
Carry extra water and have the skills and tools required for obtaining and purifying additional water, such as water purifying tablets and a water filter.
Always carry at least one water bottle/bladder.
Water consumption varies depending on current temps, exertion and how hydrated you were before starting the hike. Two liters daily is a reasonable minimum unless it is hot weather or you are hiking at high altitudes, much more will be needed, carry additional water.
Carry enough water to accommodate additional needs such as rehydration of meal packs and cooking, or emergencies such as wound cleaning.
Carry some sort of extra shelter from rain and wind, such as a plastic tube tent, space blanket, mylar blanket, or a jumbo construction debris heavy-duty plastic trash bag.
A good choice is a large rain poncho that is big enough to cover you and your pack. also, a reflective emergency blanket that can double as an aid to an injured or hypothermic person, or rain and cold shelter.