I know next to nothing of hiking, so I'd be interested in hearing of your trips and tips and whatever else!
My limited knowledge roughly amounts to go with someone (genuinely) experienced, have more water (and probably food) than you'll think you need, good footwear, be wary of the mystery berry, and don't try to pet/touch all the wildlife (no matter how cute they may seem).
Walking up a mountain to start then back down is 1/2 as hard as walking in to a valley and then climbing out even if total distance and elevation are the same. Relationships have been destroyed over such mistakes.
If you are going alone or small group. Tell people when/where you are going how long you expect to be gone what trails you expect to take and make sure you call them to report youre ok when done.
Not experienced? Don't bite off more than you can chew unless you're at least "athletic."
You don't need much to hike.
A water bottle. Plenty of water. Food is less important just have sustenance. Nuts, a couple protein bars... But man a backpack with a bladder/hose is nice. But also, consider weight.
Hiking shoes help, running shoes are totally fine. Skate shoes/chuck Taylor's/work boots will cause issues over long distances.
If it's hot, and over 10 miles, I recommend bringing a change of clothes. But again, consider weight/distance/experience.
Pace yourself. And pace your friends in your group. And speak up. Start slower than any of you feel makes sense. Get in gear. Find your pace together. Never start fast. If you're not alone, my rule of thumb is everyone should be able to have a good laugh without needing to stop. When In alone I go "slow enough I'll never have to stop". So don't push, unless like, that's the goal.
Stretch often. Before, during, and after.
Lastly, if you're getting winded, two tips:
Use your whole lungs. When people hyperventilate, they rarely use all of their lungs capacity. If you feel that "out of breath" feeling getting difficult, breathe "through your lungs. In thirds."
By this I mean full inhale, exhale about 1/3. Inhale a bit, exhale down to about 1/3 remaining, inhale a bit, exhale to 0. Repeat. This will oxygenate your blood a lot better than staying up in that top 1/3, as we instinctually do.
Hands locked on top of your head. Elbows out. Relax your shoulders. Your lungs now do not have to lift your shoulders to get a full inhale. This will help you recover faster.
That's it. Start hydrated. Finish hydrated. Stretch. Go slow. Breathe. Hiking is easy.
Hiking and pace are very mental. It's someone is slower than the rest of the group they should set the pace. You need to make sure they don't fall behind because that will make them go even slower because they will lose the friendly chit chat and get discouraged.
You want the most experience hikers on the front and back. They both are needed to keep you group together but back is the just important unless you need a good navigator. Treat it like they did the LoTR put your Gandolf and Aragorn in the front and back while you hike
Start with small hikes and work up to longer ones. If you have never hiked or walked a long distance, don't do a 12 mile hike because it will probably kick your ass for a couple days after. That carries more weight the older you get. Make sure to take breaks, hiking 4 hours straight is a lot harder than hiking 6 with a few breaks.
I know I can hike 8 hours in 80 degrees with easy terrain carrying only 2l of water and a light meal, but I also know I can't hike half that if I am going up a steep mountain trail. The only reason I know that is because I have gone past that and risked having an emergency situation. Being an experienced hiker means you know your limit and stay within it with a fair margin of safety. More importantly, an experienced hiker knows when to turn back instead of pushing further for worthless reasons. You may have to turn back and not see the top of the mountain, but you will live to try again; pushing further may mean Mr. Ballen knows who you are. No hiker wants Mr. Ballen to know who they are.
Learn the signs of heat stroke for yourself and others. Learn what dangerous animals are in the area and what to do. Learn first aid, it can save you or a stranger having a bad day.
Don't go anywhere near the staircase in the woods. Nobody was calling your name. Mountain lions screaming sound a lot like a woman being murdered, so don't investigate. If you see the guy dancing in a suit, just leave. If you feel uneasy, like you should be afraid, just leave and be on your guard. No animals are friendly, if they seem that way they are probably sick or a skin walker. Always walk away from chanting in the woods, if you hear the chanting in your head, gg. Wendigo can be kept at bay with fire, killing one means a silver blade to the heart.
If you are not going on an established trail or one that may be outside of cell service, carry two maps(one you use and another you keep safe on your person.) and download an offline map to your phone. Learn how to find north without a compass and memorize what direction roads or towns are. Wandering off-trail can be tons of fun, but it can end in a bad day if you don't know what you are doing.
A light and packable poncho(even a cheap plastic one) can save the day. Wool socks are a hiker's best friend. Wear sunscreen, especially if you are going up a mountain. Check for ticks thoroughly.
Buy walking sticks. I just got a cheap pair from Walmart for when I go mushroom hunting and my god they help out so much. I'm no longer sore and tired after a few hours out there.
This varies greatly by terrain and location, but it's easy to get lost on some trail systems. GPS is a huge help, but is limited by battery life and the amount of data the map has (heh, doesn't have) about your immediate surroundings.
Many years ago, I went hiking with a large experienced group and one of the hikers (an attractive person I was interested in) got bored with the route the leader was taking us on. She talked me into splitting off with her. Sounds like the dumb premise of a porno or horror movie, I know.
But it wasn't fun or romantic when we got lost for a couple of hours. It was scary as hell. Fortunately, we were able to backtrack to a trail junction where the main group found us again on their way back out. We got very lucky.
Nothing good ever came from that particular friendship, either. Other than learning some life lessons.
Anyway, stay with your group and make sure you have navigation well covered.
You need space between your toes and the toe of your boots. If you don't have that space, your toes will turn into blisters.
Go to REI and have them fit you for boots and a pack. Yes, you can get gear cheaper on Amazon, but getting gear that fits you right is worth the extra cost.
Plan on 1L of water for evey hour on the trail. Drink it even if you don't feel thirsty. Your pee should be nearly clear.
Buy trekking poles and learn to use them properly.
Leave your music at home, or wear headphones. No one wants to hear it.
The slowest person in your group leads.
Learn how to use a map and compass
Wear brightly colored clothing in case you get lost.
If you get lost, stay the fuck where you are. An emergency beacon is a must if you're going deep in the back country alone.
This is all just for hiking. For backpacking I have way more.
Source: Eagle scout with a few thousand hours of hiking/backpacking experience.
"Hiking" is like any other kind of outdoor activity: it can range from a literal walk in the park to scaling a mountain. You're describing hiking the same way someone who wants to get into swimming might describe preparing to cross the English Channel; if you want to get into swimming, start with a shallow indoor pool and then if you feel like it, work your way up from there.
I will say that there is a lot of misleading hiking info on the web (as in, maps of trails that are inaccurate, don't exist, or that go through private property); I'd recommend finding a book (as in, made of paper) of local hikes from your library or bookstore (if you live in an area with an outdoor store like REI that's a great resource). Select an "easy" hike of 1-2 miles from the book, ideally a "popular" hike (as in, one that's likely to have a lot of other people on it) that's somewhere within a short transportation distance, and do that for your first hike. Short, easy hikes don't require anything more than comfortable footwear, and maybe a water bottle if it's a hot day. Until you start getting into very long, very remote, and/or technically difficult hikes, assuming you're in decent health there's really very little to hiking other than stay on the trail, keep an eye on the weather, and don't push yourself beyond your limits... or more generally, "if in doubt turn around." I do recommend getting an Open Street Map app for your phone, as it's generally more accurate than Google Maps; some trails are marked better than others, and OSM is a good backup to have in your pocket if you get lost or turned around, although it's mostly only necessary if you're going into an area that has a lot of intersecting trails.
Mainly just be properly equipped for the weather/terrain. Make sure to get a decent pair of hiking boots and break them in before your trip. Socks are important, too - need moisture wicking materials, so dont wear cotton socks.
Don't bring too much food and water - i.e. Don't go overboard with it. 1 liter per person per hour is a good guideline. Be sure to actually drink it, too. Don't want to be carrying all that water weight the whole hike. Hiking poles can be really useful for difficult terrain, but they also just improve your efficiency by taking some of the weight off your legs. Bring rain gear like FrogToggs if it's likely to rain. You want to stay dry as much as you can.
If you're in the US, the national parks are really great. State parks are also a good resource. If you can make a trip out west to Utah/Colorado, the parks there are great (maybe wait until Summer's over to go to Utah, though). The northern parks are great too - Wyoming and Montana are really nice.
I love hiking. I think you've got a decent start with what you've written already.
I would advise getting familiar with navigating yourself with a map and compass, a lot of places don't have phone signal so at a minimum download your map and make sure you've got the battery to last the trip and some extra.
I definitely agree with your thoughts about carrying more water than you think you'll need, generally water will be the heaviest thing will carry but one of the most important.