Build a Town Hall as close as you can to your gold mine. Make sure you have plenty of room around it to build other structures and for your peasants to get by. Then build a farm on the lower corner of the Hall. When that's done, have the Hall make a peasant, and have your first peasant make another farm on the upper corner of the Hall. The idea is to have enough room in the middle of the farms for a Cannon Tower. Make sure the farms don't obstruct your peasant's path to the gold mine.
Step two:
Build a Barracks with your second peasant, and have your Hall crank out another peasant. Throughout all this, your Hall should be cranking out peasants, and you should have at least one peasant building a farm. You should never be slowed down because you don't have enough farms. Any time you can't train something because you don't have enough farms, you are falling behind.
Have your fourth peasant make a Blacksmith, and have all subsequent peasants use "repair structure" on the Blacksmith to speed up its completion. When it's completed, research level 2 footmen and have your peasants mine for gold. In the beginning, one or two of your peasants should be cutting down trees, and the rest should be mining gold.
When the Barracks is done, train a Footman.
Step three:
Build a Scout Tower next to your Town Hall in the space you left between your farms, and then seal it off from attack by building your fourth farm as shown in the image. Eventually, this Scout Tower will be upgraded into a Cannon Tower, but we're gonna wait a bit for that.
Keep making farms, peasants, and footmen. When the Blacksmith is done researching level 2, research level 3. Level 3 footmen will stomp all over level 1 footmen.
Step four:
If you're playing against computer opponents, your situation should look something like this by the time their first scout shows up.
Step five:
When you have five footmen built, upgrade your Scout Tower to a Cannon Tower, and go off on a raid with your footmen. Building a Cannon Tower surrounded by farms has saved my ass many times in Warcraft. While you're off on a raid, you won't have time to pay attention to your town, but the Tower should beat off anyone who tries to attack you while you're gone.
Have fun killing your opponent, who wasted time building lumber mills and such.
When attacking, position your troops between the enemy Town Hall and his gold mine to kill all his peasants. Killing an enemy's peasants severly cripples him.
If you're playing a team game, you should coordinate and attack your enemy at the same time as your teammate. Overwhelm the enemy.