Something that applies to all resource types is that a villager can carry any amount of them (unlike in Warcraft). So you can send back your hunter with 5 food if you need 5 food quickly. This is very useful sometimes. However, if you tell him to do something different (e. g. chop trees after hunting), his resources will be gone. So you had better deploy them at the nearest storage pit first. Villagers only lose resources they are carrying when changing to another type of resource gathering job. Justin has investigated this further:
Specifically, making your villagers ATTACK or BUILD will not strip them of the resources they are carrying, but telling them to go from stone-mining to gold-mining, for example, will. Also, "Hunters", which gather food from animals, can hunt different types of creatures while holding meat and not lose it.
Apparently, farming and foraging are resource compatible: Telling a Farmer to be a Forager does not cause him to lose the food he is carrying, either.
Food is crucial. You must get plenty of it to set up a decent army and get past the Stone Age. Before the Tool Age, the only chance to get food is fishing, hunting and foraging. Getting a bad starting place can screw the game. Make sure there are some bushes for foraging or fishes. The "super unit" upgrades in the Iron Age all cost very much food too.
Hunting gives a lot of food for a limited time. Make sure that all villagers on food (foragers, farmers) hunt! Since the meat decays, you must get as much as possible from it. Try to drive the gazelle to your village to make the way to the next granary/storage pit as short as possible. This can be really tricky sometimes and needs some practice. Of course you can also build up a new storage pit near the herd of gazelles. After hunting some of them, all others will run away so you will have to chase them anyway.
If you try to chase a lion, use at least two villagers to prevent casualties ;) Alligators and Elephants may look scary but they are easier to kill than lions. Beware Elephant and Lion Kings! They are truly tough, you should have at least six villagers available when trying to kill them. If possible, use one villager to lure the beast to the other ones who hide behind a storage pit.
Note that lions hunt too. This is pretty funny. In the picture to your right you see a lion that has killed a gazelle. You see what you are supposed to do with these food stealers ;-)
Foraging is the easiest and fastest way to get food. Build a granary next to the bushes and send some guys to get the berries. Unfortunately, this source is very quickly used up.
Farms are the best way to get food unless the area is very dry. It is often the only way to get enough food since the natural resources usually are very scarce. Getting past the Stone Age is crucial because then, you are independent from your natural food resources (berries, animals and fish). You have to build a market to be able to construct farms. Make sure you do not forget to rebuild farms after they are gone.
There can only be one. If two farmers work at the same farm, its productivity is not increased. You will have to build a farm for each farmer. If a farmer goes to a different farm after his own one has dried up, you will see that his productivity is next to zero. You have to build a new farm for each one that is gone.
Researching the technologies that improve your farming will make a big difference. You will see that food becomes a problem later unless you get these technologies. It is one of the upgrades I research first because it pays off soon and gets you food for more upgrades. The drawback with farming is that it is slower than other ways of getting food, but if you build at least four farms around a granary, it works pretty well. More about the placement of farms can be read at my building placement page.
By the way, farmers cannot deliver their food to a storage pit while hunters can. So make sure you build your farms close to a granary or a Town Center.
Fishing is very effective; only improved farming is better. Because you can get fishing boats without investing food, fishing is a very good way of getting food as long as the unit limit is no problem. After that point, farmers are better because you can use them for any other job if you have to. Unlike farmers, two fishing boats can fish simultaneously at the same spot without affecting each other. Thanks to Justin and Tates for reminding me.
You can get fish from some spots in the water where you see fish jumping around or a whale. Just right click on that area when your fishing boats are selected, and they will take the 300 food that the area yields to your dock.
Wood is pretty easy to get. You should build a storage pit near a forest and then send them villagers to chop wood. It is a good idea to use the forest as a wall, so make sure you do not chop through it before you are prepared! Try to wall off your villagers chopping wood because it is hard to protect them (your host will probably be within the town while the forest is a bit further away).
You will need 200 wood for most of the buildings, and building up a navy also costs very much lumber. Never forget to build houses for your increasing population; if you have not enough houses and even have to wait for wood to build the next house, you have screwed up the game. Houses are some kind of a fifth resource in Age of Empires. In the Tool Age, the balance between using villagers to get wood for farms or to build farms and houses (using your wood) to get food and living space for more villagers and troops is the most important aspect of the game.
Gold becomes as important as food in the later game. Priests cost a lot of gold. Gold mines are a good source of gold but they run out pretty soon. Researching coinage increases the productivity of a mine by 25%, i. e. you will get 375 gold instead of the normal 300, so research it if you have still more than one mine going.
With trading, you will get enough gold to build up a strong army in the Iron Age. Make sure that you have not more than two merchant ships per dock because more merchant ships will not bring in more gold. You can always see how much gold is stockpiled in the dock. It is the upper number that is indicated, in the picture, it is 84. It cannot be higher than 100; if it is above 50, sending two ships to the same dock does not decrease their performance. If that value drops to zero, send your merchant ships to a different dock because they would have to wait a very long time to get a full load of gold. The lower number is not that important, it means you will get 11 gold for 20 food. Do not worry if your merchant ships are under attack, they can take quite a few hits. If the hit points are getting low, repair your ships. Always trade food or wood, never stones! Stones are as hard to get as gold, and you cannot trade for them. Once the stone mines are emptied, there is no way to get more stones. Food is almost unlimited, and if your infrastructure is good, you will get enough food to trade it for gold. Note that the player who owns the dock does not get anything from the trade.
Stones are only used for towers and walls. Towers are pretty expensive (150 stones) while walls are very cheap (5 stones per tile). At the beginning, you will perhaps not even be able to afford a tower (you can either build a tower or walls at the default resource setting). You should raise some walls as soon as you can to make it easier to defend your town. Always keep some stones (10+) in reserve so you can repair your walls and towers if necessary.
This feature is hardly used for paying tribute to enemies but rather for trading resources among allies. Use it! I use it quite often, and it can be crucial if your ally gives you some food that lets you advance quicker through the Ages. After getting Coinage in the Iron Age, you will not even lose the 25% resources any longer! This will make it possible to get the "Super Units" upgrades (e. g. Juggernaught) much faster. Concentrate on the next upgrade, then get and trade resources until you can afford it.