Your character needs to eat in order to survive. It is easy for a new player to starve to death if their stamina is low and if they get wounded. If you want your character to stay alive keep him/her well fed until you learn how quickly stamina and healing drain your hunger bar.
Your attributes are based on the food you eat. You gain strength, charisma, dexterity and your other skills from your choice of food. This means that if you rely on only one or two foods your attributes will get out of balance. If you eat only chanterelles and blueberries you will get high dexterity and high intelligence but all your other stats will lag. You need to eat fep equal to the number of your highest attribute to gain in any attribute. So if your dexterity is 20 and you need to gain strength because it is still only 10, you will have to eat 20 fep to go up to an 11 in strength. If your attributes get badly out of balance it is extremely hard to raise the trailing stats.
You will probably eat a variety of different foods so your fep bar will show several different colours. If your fep bar shows 2 fep of strength, 4 fep of psyche, 3 fep of dex and 1 fep of charisma and you need to eat 10 fep to gain any attribute you have a 20% chance of gaining strength, a 40% chance of gaining psyche and so on, proportionate to what you have eaten.
Every new player can do this:
Look for Apple, Hazelnut, or a Mulberry trees, found in broad-leaf forests. If you find one, right-click it to pick a fruit, which will then appear in your inventory. You must have at least one empty tile in your inventory to do this.
Then right click on the fruit for the option to eat it. If you eat an apple, you will have to drop the apple core to empty space in your inventory (or on the ground). Each tree only produces a certain amount of fruit at a time, and fruit doesn't help increase your attributes, so try not to rely on them for too long. Once you decide to venture outwards, though, make sure to have some surplus food in your inventory.
You also might be able to scavenge fox kills. Foxes kill rabbits. The most common place to find a dead rabbit is at the edge of the water, where rabbits often become trapped. Foxes also kill chickens. Chickens are found in grasslands, moors and heaths. When a fox attacks them, they scatter; so if you see chickens running around, there is a good chance a fox has been hunting them, and you might be able to find one or more dead. Fox-killed rabbits and chickens are just the same as ones that you kill yourself, except that you don't need to have the hunting skill to make use of them.
If you get the foraging skill:
Raid Ant Hills. You also need the hunting skill for this. Just right-click on the red mound near ant swarms. The option "Raid" will pop up. If you have 10 Unarmed Combat skill, you should be able to withstand their blows til your character is done raiding the ant hill. If you find an ant hill near water, you can press the raid button, and quickly walk into the shallows. Wait til the ants touch the shore and walk back out. The ants will be walking around not noticing you, but you will still be aggroed, and you can go raid the ant hill. All items found when you raid an ants' nest are food, or curiousities. Not all ant hills will have items in them. Sometimes, an ant hill will have several items in it. WARNING: ANTS CAN KILL YOU! They only attack once each while your KO'd but it can deal serious HHP Damage and death.
Look for Chantrelles. These are pale orange speckles found in forests on the ground. Look for Spindly Taproots, although eating them might be a waste. These are dark brown roots that grow in forests on the ground. Right click them to pick them. Look for blueberries. These are plants that grown in forest or on heath or moor. (Higher exploration and perception enable you to find more.)
If you have the hunting skill:
Look for rabbits. You need at least four empty tiles in your inventory in a 2x2 square. Get as close as you can to a rabbit. Wait until it stops moving and stand exactly beside it, but so that the rabbit is still visible to click on. Right click on the rabbit.
If it runs away and you missed it, immediately click the round button with crossed swords beside the picture of the rabbit that pops up in the top right corner. This will stop the aggression between you and the rabbit, and it will soon stop running away, giving you a chance to find it and try again.
You will need to right-click on the rabbit in inventory to wring its neck, and then right-click again to butcher it.
In some terrains, you can try to find chickens, too. They are caught and killed the same way as rabbits, but are easier to catch.
If you have a sling:
You can attack and try to kill larger game, such as foxes and deer. They will not attack you until you attack them first, so you can fence them in to make it easier and shoot at them safely from outside the enclosure. Hunting enclosures are usually made out of fires. Just put one branch in, and then move on to make the next fire. It will make a row of little signposts that the animal cannot escape. A good place to enclose an animal is just at the edge of water. They often stop there, and it takes fewer fires to enclose them. Foxes are the easiest to kill, followed by boar, although boar will attack you. You may want to hunt boar from a boat or after enclosing yourself next to a boulder. Deer will not attack you unless you attack them so they are easy to trap. However, deer will heal animals that you are fighting; if you try to kill one of a herd of deer, the other deer will keep healing it, making it harder to kill.
Aurochsen and mouflon are not good quarry to practice on, as they mob you if you attack one of them. You will need to enclose the entire herd, with your target animal enclosed separately from the others, to remain safely out of their reach.
By using a boat, you can safely attack any animal as long as you keep just out of range. This is one of the better ways to hunt aurochsen and mouflon.
If you have the farming skill:
Sometimes you can find Wild Windsown Weed which can be dried to different seeds. Carrot seeds can be planted for Carrot that can be eaten (or planted again) raw. Grapes can be eaten raw too but you will not be able to replant the seeds until you have the winemaking skill.
If you have the fishing skill:
Fishing is not a very good first option. You will need to have fishing line (string), hooks, a fishing pole and bait or lures. Hooks require bones, which usually require hunting or scavenging animals. Spindly Taproot and other plants function as string, so foraging is required. If you have carpentry, you can make a woodfish lure from a wood block (made out of a tree stump or log). If you have Stone Working, you can make a rock lobster lure from a stone you chip off a boulder. Unless you can make a lure or find leeches, you will need to dig in the dirt to get earthworms for bait; this uses a lot of stamina, and thus may make you hungrier than whatever fish you catch.
Fishing is done in waters where fish can be seen. If you don't see fish jumping out of the water every few seconds, there are no fish there.
While fishing is not the easiest option for a single player, it is probably the best starting skill for a group of players located close to a lake or a river. Dividing the necessary tasks (1 hunter, 1 forager, 1 stoneworker, 1 lumberjack-carpenter) allows for the steadiest income of food possible without relying on luck to find prey or edible plants.