The Move-Order is the most used and probably also the most versatile command.
You can combine move with various keyboard-keys or drag a line or queue up commands while holding down SHIFT very easily.
Simple Right Mouse click. Move (hotkey: M) instructs units to travel to a waypoint. For factories, this sets a waypoint for units it constructs. Right-click on the map to give a move command to your selected units.
Move in formation
Ctrl + Right Mouse click wil let your move units in formation. Faster units will move at the speed of the slowest units in the group.
Move Line Drag
Right Mouse + Drag to "draw" a custom formation. Selected units will be given waypoints evenly spread along the line you drew. See, BAR is for artists too! So-called "custom formations" are the best way to spread out your units.
Move Line Drag is superior because:
A) you can avoid splash damage
B) you can put your units where they can shoot the enemy.