I feel that food can be divided into two categories: That which crawls; That which sprouts. First, I'll cover plants, then I'll say some about ways to get meat.
Growing, Catching, and Preparing Food - An Overview 
If you are facing the prospect of gathering and / or catching food in the wild, you are facing one of two circumstances: this is a lifestyle choice, or you're in a long-term survival situation, where chances of rescue within weeks are slim.
The time frame of weeks may surprise some, but the reality is that in most survival situations, food is the least important factor, i.e., if you make it your number one survival priority, you'll probably get killed by something more important like not having sought adequate shelter while you were chasing badgers with a pointy stick. But getting down to brass tacks...
Chances are, you're not going to develop the skills necessary to hunt wild animals without firearms in any immediate timeframe, so the next option available to us is to prepare snares and traps. Snares and traps have the distinct advantage that they are hunting for you night and day, rain or shine. A simple circuit of your traps once a day is all that is required. The most important, and hopefully obvious consideration with traps is site selection: place traps where animals will be. Bait is fine, but to have bait, you have to have already caught something, haven't you? If you haven't, consider that animals invariably seek water, so a simple snare along a well worn path to the creek is perfect.
Types of Traps:
- Cage Traps
- Fishing Lines
Edible & Poisonous Wild Plants 
Here are some guideline for eating wild plantlife. In most situations, if you don't know what a plant is, don't eat it. You can live 3 weeks or more without food. You can live a lot less long with poison in your system. Only eat wild plants if you have devoted a good deal of time to studying them.
- Do not eat mushrooms or fungi unless you know for certain that it is edible. Most are poisonous, and there is no way of determining which ones are edible without properly identifying the species.
- Plants with umbrella-shaped flowers should not be eaten.
- Avoid legumes (beans and peas).
- Bulbs should generally be avoided. Wild garlic and onions are edible but have poisonous look-a-likes. However, garlic and onions smell distinctively like garlic and onions.
- Avoid white and yellow berries, as most of them are poisonous. Blue and black berries are usually safe to eat.
- The "berry rule" is that 10% of white and yellow berries are edible; 50% of red berries are edible; 90% of blue, black, or purple berries are edible, and 99% of aggregated berries are edible. This is only a guideline, and unknown berries shouldn't be eaten.
- Aggregated fruits and berries are almost always edible (blackberry, raspberry, salmonberry, and thimbleberry).
- Single fruits on a stem are usually considered safe to eat.
- Plants with shiny leaves or a milky sap are considered to be poisonous. The two that don't follow this rule are Dandelion and Fig. (Both have milky sap.)
- It is a myth that if an animal eats something, then it is safe. For instance, deer will eat poison ivy.
- Wild nuts that taste or smell like almonds are EXTREMELY dangerous. They contain hydrogen cyanide.
- Wild fruits and berries can be checked for edibility in the following way:
- Put a small amount of juice on your forearm and wait until it dries. If there is no burning, swelling or redness go to the next step.
- Put a small amount of juice on the corner of your mouth and wait until it dries. If there is no burning or stinging go to the next step.
- Put a small amount of juice on your tongue. If there is no burning or stinging go to the next step.
- Eat a very small amount. (If you immediately feel sick or vomit, stop eating!) If no symptoms occur in 24 hours, the item MOST LIKELY is not poisonous.
- Eat sparingly at first, and if symptoms still do not occur, proceed to eat as much as you like.
NOTE: This technique can be very dangerous. Many plants (Agave, to name one example) contain compounds that won't burn or tingle, but can be powerful emetics and/or laxatives. Others may be safe in small quantities, but can be dangerous when large amounts are eaten. Your best bet is to familiarize yourself with a few common plants for your area that can be eaten, and not rely on potentially dangerous methods such as the one listed above.
There are three main types of meat you can get in a survival situation: Insects, fish, and game. Here they are covered in that order; easiest to hardest.
All mammals and birds are edible. Some must be boiled or roasted until tender, though.
Do not eat dog/wolf liver, it contains high levels of vitamin A which can lead to hypervitaminosis and death.
Eating a long term diet of only rabbits can lead to "rabbit starvation" and death. Rabbits have no fat which your body needs.
In many places, insects are a staple of local diets. Some basic guidelines for insect eating:
- Avoid brightly colored insects.
- Avoid insects that bite or sting.
- Avoid fuzzy or hairy insects.
- Most worms and grub are good to eat. It helps to toast grub until they are dried.
- Some ants are good food. Dip a stick in water after letting it be coated by ants; repeat until you have enough.
- Before eating grasshoppers and crickets, remove their wings and legs. (They scratch on the way down.)
- Only eat fresh, healthy insects.
- Grasshoppers can contain tape worms, grab them behind the head and hold their body and pull out the stomach and intestines, and it is a good idea to line them up on a small stick and roast them on a rock by a fire.
Fish are easier to catch than wild game. It's best to go fishing in the morning and at dusk; just after sunrise and before sunset. In streams, look for deep still pools, undercut banks, and the areas around and behind sandbars. In lakes, bass gather around cover. Try areas around plantlife, sunken logs and boulders, docks, and areas around dropoffs and ledges. In the ocean, try reefs, points, deltas, and channels. Here I have listed some ways of catching fish, along with how to use these ways to catch various types of fish:
Common Types of Fish 
- live in lakes and ponds. They like warm, clear, slow-moving water. They gather around cover (as mentioned above). A predatory fish, they like large worms, frogs, liver and other organs, crickets and grasshoppers, any meat, and crayfish. They average about 2-5 pounds. Bass weighing 8 pounds or more are uncommon, but not unheard of.
- are bottom feeders living in lakes, ponds, channels, and slow-moving rivers. There are also saltwater species. They like deep water, and will eat anything strong and smelly, such as meat, organs, and cheese. They have even been caught using things such as bubblegum and cottonballs soaked in meat juices. They are also one of the only fishes that can caught by noodling. For using a rod & reel, put bait and a heavy weight on the end of you line. Then, throw it out into the deep water at the middle of a lake. Let it sit there until a catfish comes across it. As for weight, they are usually around 2-5 pounds, though the biggest on record was 646 pounds!
- are small fish sometimes called panfish and bream. They are caught on either flies or live bait. They gather around underwater vegetation. The average weight is a pound or two.
- Rod & Reel
- Using a rod & reel is one of the best ways to catch fish. You can use it in the normal fashion, or use the line and hooks to make "set lines." (See below.)
- Nets, when properly placed, can provide a wealth of food. Lay one down in a creek with a line tied to each corner. Wait till fish swim over it, then lift it up. Also, try tying one under a waterfall. As fish pass over the falls, they get caught in the net. Also a "gill net" consists of thin strands of material making a "curtain". When fish take water in through their gills, they draw in the strands and suffocate.
- Set Lines
- Your time can be used more efficiently by setting many fixed lines from things such as tree branches overhanging water. This is the same technique used by trappers; rather than hunt one animal at a time, they set dozens of traps, increasing their odds of catching something.
- Fish can be harvested with a spear. To make an improvised fishspear: Find a long, strait pole or piece of bamboo. Wrap a piece of cord (tightly) around one end, about a foot from the end. Split the end of the pole evenly in half. The split will stop at your cord wrap. Sharpen the two points. You may also fire harden them.
- To use it, stand perfectly still in waist deep water. If you have bait to spare, you may scatter some around you if you wish. Keep the spear-point in the water and move it VERY slowly towards a fish. When your point is a foot or so away from it, jab it sharply, pinning it to the bottom. Try to make the fish slip between the two points, wedging it. Wedging it is better than piercing it; stabbing it can mess up the meat. Now, reach down and grab it firmly; as long as it's still in the water, it can fight with amazing power. Throw it on the bank and continue fishing.
- You can construct fishtraps out of vines, bamboo, wire, or plastic jugs. As a rule, the time it would take you to construct a fish trap (if you could at all) is best spent on other things. However, I'll still include directions for their construction. To make a simple fishtrap from a large narrow-mouthed plastic jug: Cut the top few inches off of the jug, widening the hole just enough allow comfortable access for a fish. Then, cut the top third off of the jug. Invert the removed section, and stick it in the rest of the jug, creating a funnel. Secure it in this position. Put bait in the jug. Fish will be "funnelled" in towards the bait, but will be unable to exit. You are actually more likely to catch crawfish and lobsters than fish with this! The same design is used to make woven and wire traps. (If someone knows the exact way to weave traps, put it here!) Also, on a beach, you can build a fishtrap from logs and stones: When the tide is low, create an inland-facing halfcircle of logs and stones. The tide comes in, and the trap is submerged. When the tide goes out, fish a trapped in the halfcircle as the water level drops. They may then be picked up.
- Fishing Poisons
- There are some plants that deoxidise water (remove oxygen). When added to a small pool of still water, they cause fish to suffocate and float to the surface. Because you did not actually poison them, there is no danger when eating fish caught this way. (List of plants has yet to be added.)
- With practice, you can actually catch fish by hand. When you catch catfish in this way, it is called noodling. (Catching catfish uses a special technique, not covered here.) To catch fish by hand: Find an undercut bank over still water. Laydown on your belly on the ground next to the water. Stick your hand in the water. Move very slowly and gingerly until you feel a fish. Work your hand under his belly. Grip firmly and lift him out. This is kind of like spearfishing with your hand. It takes a lot of practice.
Older people have mentioned tickling the fish, then jamming your thumb into the gills for extra grip.
Next Step 
Now that you have a fish (or several fish) you should scale and clean them. (Instructions for scaling and cleaning to be added.) You can eat the heart and liver. Save the other organs for bait. Cut open the stomach to see what the fish has been eating, so you can get an idea of what bait to use. If the stomach is empty, it means that the fish are very hungry, and will bite almost anything. You can put the head on a large hook and drop in the water to catch a snapping turtle. Scatter whatever is left in the water to attract other fish.