Food preservation
Food preservation is important, but it's also a complex topic. There are a ton of different ways to keep your food from spoiling. This guide will broadly cover a few big ones.
Freezing
This one's easy. If you have a freezer that's plugged into a power grid, or if it's below freezing, you can just leave items in the cold and they'll freeze. Items that are frozen will take a very, very long time to spoil.
Refrigeration
If you can set up a power grid and get a refrigerator running, items stored in it will go bad much more slowly.
Zipper bags
Zipper bags make items go bad about 10% more slowly. This isn't a lot, but it can save a sandwich or two, and it stacks with other methods listed here.
Smoking
The most significant thing you can do to boost the shelf life of your food is to build a smoking rack via the construction menu. At the time of this writing it only takes 3 fabrication, 2 food preparation, and some sticks and rocks. You'll want a charcoal kiln as well so you can keep it fueled up.
To use the smoking rack, examine it, fill it with charcoal, insert your food, and once it's all ready to go, light it up and walk away. In several hours, the food inside will be smoked, vastly improving their shelf-life.
Most smoked items can go through the process again, becoming dehydrated. This preserves them for much longer.
Canning
Canning is done via the crafting menu, and will generally require a canning pot. Many items can be canned, including vegetables, meat, soups, and a bunch of other stuff.
Jerky
Jerky is one of the lamest ways to preserve meat, only adding a couple of weeks to its shelf-life, but it's also the easiest. All you need is 3 food handling, a chunk of meat, some salt, soy sauce, seasoned salt, or pepper, and a way to cook food - even a campfire will do the job.
Rendering Fat
Something most of us don't do in our day to day lives, but that was very important to our ancestors, is rendering fat. Well, society's gone, so we're back to basics.
Fat can be rendered by crafting it into tallow or lard. Tallow and lard are more or less interchangeable, but the tallow recipe is more efficient. Lard on the other hand will produce cracklins as a byproduct, which are basically fried bits of skin and fat that are pretty tasty and can stand in for meat in several recipes.
Tallow and lard have a very long shelf-life and are useful in a ton of different crafts, not all of which are food. One of their most important uses is as a component of pemmican, which is one of the most convenient and long-lasting food items you can make.
If you are cooking mutant meat, make sure you don't eat any of the fat, as it tends to have a much higher concentration of toxins than the other parts.