The Long Dark Long-Term Survival Strategy

Always start in Mystery Lake.

Mystery Lake

• Your first priority is warm clothing. At first wear anything that's warmer than what you got, then worry about efficient weight-to-warmth ratios once you can comfortably explore through most temperatures.
• Your second priority is setting up a home base from which you can store your goods, craft and cook. The best candidate by far is the Camp Office on the edge of the lake, as it has a relatively central location, is on the main transit route through the map (the railroad) and it has a bed, indoor fireplace, workbench and containers.
• Your explorations should focus on visiting each area of the map, collecting all of the loot and storing it all in your base like a pack rat. Ideal locations to hit first (besides the Camp Office) is the Forestry Outlook (possible weapon spawns), Trapper's Homestead and Logging Cabins. Additionally, one loop around Mystery Lake and a browse through the cabins will likely net you significantly better clothing (often you find a Down Ski Jacket or Mariner's Peacoat).
• You should make sure you hold onto a hatchet and a knife. Hatchets are great for foraging wood (which you will do a lot of) and knives dramatically improve your ability to fight off wolves (this will also happen a lot).
• Hopefully you will find a rifle and storm lantern by now and are ready to tackle the Carter Hydro Dam. You can still do it without a rifle, but it's a bit more dangerous (you should definitely have a knife). Head to the dam and take off your clothes upon entering (in case you struggle with Fluffy) and kill Fluffy if he's in the dam. Once he's dead, loot the Dam freely but do not leave the dam through the lower door. Accumulate the gear by the doorway or the fire barrel on the turbine floor. Cook, eat, rest, and get ready to start lugging the gear in one or two trips back to the Camp Office.

Coastal Highway

• Eventually, either due to boredom or running out of resources (especially bandages, clothing or ammunition) you will want to explore more. Your next goal is the Coastal Highway, but before you begin you will want to prep accordingly.
• Set up a mini-base in the entrance of the Carter Hydro Dam. I suggest plopping down a bedroll, half a gallon of water, 1500 calories of durable food and medication to treat every possible condition. This base is to rest at before you proceed forward (the Coastal Highway entrance is right next to the Carter Hydro Dam).
• The Coastal Highway map is quite dangerous due to the wolf density, close corners and uneven ground. It's difficult to navigate and there's no good location for a base, so our plan is to loot the map and lug everything back in stages to Mystery Lake.
• When you're ready, go through the Ravine next to the Carter Hydro Dam. Make sure you have a decent amount of food (though you can find food easily), plenty of water (it's much more time-consuming and dangerous to make water), medication for struggles, prybar, can opener, and your rifle/hatchet/knife as usual.
• Your general plan is to loot each location, collect the items in the Log Sort, and repeat until you've cleared the map. After the map is cleaned out, move the gear from the Log Sort back to Mystery Lake. If you ever get in over your head, just go back through the Ravine and you can recuperate at the Dam (see why we built that mini-base?). If something really bad has happened (e.g. out of ammo, depleted all your food and water) you can use the resources at the Dam to rest a night and make it back to the Camp Office the next day to rebuild your reserves.
• Remember: you are not here for food. Food is far easier and safer to obtain in Mystery Lake. Always prioritize taking useful items (e.g. scrap, cloth, tools) over food. Only carry enough food to keep you alive with some emergency leftover. If you have to shoot a wolf, I'd generally discourage you from even bothering to harvest it. Taking the meat means you need to spend more time gathering wood and cooking it, and then more time to boil water since you're staying longer... and there's no safe, good place to do any of this.
• Use flares to fend off wolves. Don't even hesitate- that's what they're there for. Since you have no intention of harvesting them, it's pointless to kill the wolves. Then again, shoot the wolf if there's any doubt about whether you can get away safely, or if it's blocking a key loot location. Don't forget you can also drop food (default is the "4" key) to distract them. The raw meat you find in fridges and freezers are excellent decoys.
• This is probably obvious, but don't mess with the bears.