Stop-Move:
If
you're a fast clicker you can take advantage of the projectiles
slow speed. Learn which units "predict" their
shots, and dribble them. Yeah, dribble. A great example
is the heavy gun. That thing's shot is amazingly strong
and its range is very high, making the heavy gun easily
wipe out most attacks - *if* its units moves linearly. To
easily put down one lonely heavy gun (ie. nothing around
it to help), simply move a fast unit, say, a jeep or a light
tank in its direction, and instead of letting it move by
itself, everytime you see the heavy gun shoot, slightly
change your unit direction - but still progressing towards
the target. What happens? Since the heavy gun calculated
your direction and speed at the moment of the shot, it'll
miss the shot because you moved the unit somewhere else
after the prediction. There are two things you must keep
in mind while using this technique: terrain and splash area.
Of course if you have to climb over a tight path to get
to the heavy gun, you'd better stop, since you don't have
any other direction that gets you closer to your target
and away from the shot's splash area. Anyway, this is a
valid technique that works against mortars and medium/heavy
tanks. Unhappifully it's severely detracted by the click-move
lag that's inherent to Z:SS 3D pathfinding calculations
(more in the Z:SS FAQ section).

Who
told you heavy guns don't miss their shots?
Move-Shoot:
Robots can't move and fire at the same time. Differently
from the tanks, they have to stand ground to start attacking
something. You must keep that in mind at every combat, because
it's crucial to maximize the projectile units (mortar, medium
and heavy tanks) performance. For example, if you have just
one mortar and make it right, you can kill piles of toughs
if you have LOS. How? Simply keep moving the mortar slightly
away from the toughs at each shot it fires. Everytime the
toughs get in range they'll take a split-second to aim its
weapon, and then it's time to move your mortar again. Meanwhile
you kill the toughs along the large mortar plasma shots'
splash radius. It works like a charm, too bad the click-move
or the internet lag makes it a hard technique to get the
grip of.

1)
Come toughs... 2) die toughs... 3) Back to 1! :)
Next: Defenses