Goliaths are a very powerful, yet underused unit in the Axis arsenal. The Wehrmacht and Panzer Elite Goliaths are identical in stats, and both cost 125 munitions. For the Wehrmacht, you can produce them from any bunker (including base bunkers), for the Panzer Elite you can drop them from Vampire Halftracks that are built from the Logistik Companie tier 1 building. While Goliaths are expensive, when they are detonated they explode with equal or greater power to artillery shells, while being able to be positioned exactly where you want to create maximum damage.
Goliaths can cloak when in yellow or green cover. To do this, just move your Goliath into the cover and it will cloak in about five seconds. No units, even detector units (Jeeps, Recon Squads, etc) can see the Goliath when it is cloaked, so you can position it and forget about it until the right time comes along.
When to Strike
Choosing the best moment to strike is very important, as Goliaths are a hefty investment.
Make sure your target is close enough so that you don't end up chasing it too far and your opponent noticing, and retreating his squad before impact, or even worse, focus firing on your Goliath and destroying it.
Make sure there are no obstacles in your path to the target, or it will slow down to traverse, or go around, giving your opponent time to kill it.
If your opponent spots your Goliath and retreats, don't try to kill the retreating squad because they will be more spread out and you are unlikely to kill every member.
This is hard to do, but try to strike when your opponent isn't paying attention, perhaps set up your ambush away from your army so he doesn't expect any resistance. Try setting up close to his base and catching squads he has given a move command to the forward lines, he will not be looking.
Don't waste 125 munitions trying to take out a full health tank. Unless the tank is on less than 50% health, save the Goliath for later.
If you know your opponent has an anti-tank guns or infantry nearby, be careful as these can take out your Goliath before it has reached the target.
Place the Goliath on your opponent's side of cover; when he goes to use the cover, he's in for a nasty surprise.
If you're producing out of a non-upgraded bunker, you can set the rally point for the Goliath, and it will go there after it has been produced. Set it so it moves into cover and hides itself automatically.
Goliaths are also very good against direct-fire emplacements (i.e. not Mortars or 25-Pounders), and can be used very effectively against British players to soften their anti-tank capabilities before bringing in your own tanks. A Goliath will kill a 17-Pounder in one hit, even over-repaired, unless your opponent has Improved Emplacements. If your opponent has set up his emplacements close together, try to place your Goliath in the middle for maximum damage. Also, be wary of 17-Pounders, always approach from a direction that the AT gun is not facing, because they will snipe the Goliath in one shot.
Below is a video demonstrating some tips and ideas on how to use Goliaths, and how effective they are against British emplacements. Here is a summary of the video:
Goliaths are undetectable to any enemy unit, including detector units.
Always rotate your Goliath so it doesn't have to turn before advancing on the target.
You can use Goliaths to clear large holes in hedges so that your AT guns and Flaks have a longer range.
Attack the side of garrisoned houses with the most windows, to ensure maximum amount of kills.
Goliaths kill over-repaired 17-Pounders, Vickers Nests, and Bofors in one hit.
Goliaths do about 50% damage to Mortar Pits, 25-Pounders, and Churchills.
Improved Emplacements means you need two Goliaths to kill any emplacement.