-Get a heavy hammer and hacksaw ASAP. If you spawn in Pleasant Valley, there's a good chance that you'll find at least one of the two. The most logical places to look for the hammers in Pleasant Valley are the basement of the Farmstead house, the Big Red barn, or the Signal Hill outpost. If you spawn in Timberwolf Mountain (provided you don't die from hypothermia, fall damage, or a wolf attack) you can generally find a hammer around the work bench. I don't think I've ever found one in Desolation Point if I've spawned there (probably for game balancing reasons; the developers don't want you crafting tools on day 1), but check the Riken and Hibernia Processing Plant. Hacksaws are pretty common wherever you can find workbenches or large tool chests. Also, only go to the Forlorn Muskeg forge if you have a death wish.
-Fishing is a great source of food, but you have to know how to do it well. First off, you need fishing tackle, which has to be crafted using line and a hook. Hooks are easy to make as they only require scrap metal, but lines require cured guts, which take days to cure (occasionally you can find one in a tool box). I'd suggest trying to find a Frozen Angler book and reading it in order to get your skill from Level 1 to Level 2, as fishing on Level 1 has a good chance of breaking the line which you spent days waiting to make. Always make sure to have enough firewood and water for 3+ hours of fishing. You'll also need something to break the ice on the fishing hole, so keep a crowbar, hammer, or crafted hatchet/knife on you when you go fishing.
-Cat tail stalks are a great food source. They provide 150 calories per stalk and almost never decay. They're also super common; you can probably find 10-20 on the Mystery Lake. If you have 40 cat tail stalks, that's around 6000 calories, or almost a week of food if you follow the Starvation Method. Speaking of which...
-The starvation method is the best (and in my case the only) way to play Interloper and have any chance of lasting longer than a week at most. Starve all day. It will only reduce 1% condition per hour, which you can regain by getting as tired as possible (around 12 hours of sleep required) and eating 900 calories and drinking water. Then, sleep for 10 hours and take a drink, and go back to sleep for 2 more hours. The cumulative condition restoration effect of sleeping 10 hours straight will yield a whopping 55% gain (if I did my math right).
-When hunting wolves, don't alert them and try to shoot them with the bow as they're charging you; more often than not you're gonna wind up dead or dying. Instead, what you want to do is try and sneak up on them, so you have a better chance of hitting your target. Also, aim for the head, and don't be surprised if it takes more than one shot to down them. In that respect, keep enough distance that you can run if needed.
-I don't have much experience with hunting bears or moose, but I can tell you this: you're gonna need a hefty amount of arrows to take them down, and you're gonna need a good sniping spot (so get good with the bow). If you can, get to a spot that they can't access (such as a ledge that requires you to cliff-ride down). Other than that, you're on your own with that one.
-ALWAYS keep a heavy hammer on you if you can. It's arguably the best tool to use in a close encounter with a wolf. Just select it during the "select tool to defend yourself with" prompt, and spam the heck out of that LMB. They'll generally get scared off pretty fast.
-You can sometimes find a fire striker. The only two places I've found it are behind Jackrabbit Island on a corpse, or at the Hunter's Blind in Mystery Lake. The tool provides a higher chance of starting fires, and allows you to save those precious matches for another day.
Those are just some of the tactics I use when I play Interloper. If I had the time or the energy, I could probably double the size of this list. Good luck, and have fun. *Also please note that I wrote this while I had a concussion, so if some of the grammar or spelling is off, I'm sorry.