Age of Empires III Walkthrough

1.0  Before Playing
Master the following:
1) Groups.  Select the units you wish you group.  Hold the Ctrl key and press a
number key.  Now the units are associated with the number key.  To select the 
grouped units once again, simply press the number key they are associated with.

Use groups to separate your unit types.

2) Attack-move.  Hold the A key and left click your destination.  Attack-moving
commands your units to attack any enemies they encounter while moving.

Always attack-move.

3) Some units have special abilities.  They are powerful.  A selected unit's 
special ability--if it has any--can be activated by pressing the appropriate 
icon in the menu in lower right hand corner of the screen.

Use special abilities often.

4) When choosing cards, select artillery cards, the Fort Wagon card and the 
Factory card when they become available.  Some of my strategies depend on these
cards, and they are some of the best to have.  When choosing any other card, be
sure you need it.  In the campaign mode, cards that improve resource collection
or decrease building costs are useless, while military unit cards are priceless.