Here are some tips to keep in mind when using a Bertha or Intimidator:

Don't put your Bertha next to anything you don't want to destroy if the Bertha blows up, and once you start firing it, your opponent will do everything he can to make sure the Bertha gets killed. Don't let your own Bertha wipe out anything significant in your own base too.

Jam it with multiple jammers so after your opponent's first retaliation, if one jammer goes down, you still have some very small protection. The jammer is the first unit to send to the location you'll build Berthas at, and everyone else who drops in should have a jammer escort, as well as everyone who leaves.

Try to have plenty of construction vehicles and maybe a construction aircraft or two building it as quickly as possible. You want to get in and out and get it ready as early as possible. If you have the resources to build two at the same time, do that, and build them in different places so that if the fire of one is blocked by an obstacle, the fire of the other just might make it past.

Build defenders like crazy around the Bertha, and some laser towers if you have the chance. You will be attacked by air immediately upon firing by anybody with any kind of air force at all. Also, defenders and fighter patrols wandering in a confusing
pattern to the side of or in front of your berthas can spot the scout planes he sends scouting for the Berthas, if he does so. This could buy you some vital time to shoot the Bertha more, and defenders are incredibly cheap, so don't be stingy.

Berthas and Intimidators take a lot of infrastructure to build, so try to be building Fusions and perhaps Mohos, if you can, as quickly as possible. You need neither, but you don't want to wait for your Bertha to fire, and you don't want building it to eat all of your resources.

An Intimidator needs energy storage -- NOT ENERGY PRODUCTION -- to fire, so try building two energy storage units per Intimidator. This is also a very good idea for Bertha if you are building early, so you have the storage units to give you enough
reserve power to fire off the Bertha quite a bit without slowing down or slowing down the rest of your base either.

People often scout and attack monotonously back and forth along the same lines, so try to put your big gun where the enemy isn't.

Berthas are more useful on small maps, so use them there yourself, again in an unexpected location that your enemy doesn't seem to scout. On big maps like shore to shore, put a big gun on the island close to your enemy's shore, if you can. On metal isles, a Bertha at the edge of your base will fire to the edge of his base, but not inside. An Intimidator will make it around halfway into this base. Try to remember which maps a Bertha was too short for but an Intimidator worked with. Remember how terribly inaccurate Intimidators are. If you can, build two so that accuracy counts a little less.

When targeting, getting off shots quickly is imperative because retaliation is imminent, so try not to make your Bertha have to turn much or at all to fire at multiple targets. Try to fire along the line of the barrel, not side to side, if possible. Berthas turn awfully slowly. Unless especially rich targets demand it, fire up a radius first, then fire to the side. Remember to try to hit targets that explode viciously, damaging or destroying other targets when they go. High-level units destroy other units when they die. Including your commander, so keep him well back.

Try to queue up many targets at once; once your Bertha fires, you'll want to be watching very carefully for retaliation, not clicking with Bertha. Bookmark where your Bertha is and where you're firing so you can alternate between the general areas (CTR-5 through CTRL-8). Put your Bertha in a control group that's easy to find quickly (1 or 9). This way you can turn it off quickly if energy gets too low, or target it quickly if something new pops up.

Keep two construction vehicles by each Bertha. One should be set to guard the Bertha so you can keep on killing, and the other should replace defenders that get taken down by attack, and then move on to repairing and replacing other units.

On naval maps, some people can't figure out where the big explosions are coming from and think all big explosions are Berthas. It could be a conqueror cruiser, too, though, or a ranger missile boat.

Watch very carefully if your Bertha fire is hitting uselessly into the side of a mountain or terrain feature, or just causing no explosion. Make corrections immediately.

When firing blindly, watch the area you're aiming at (use "T" to follow the bertha fire if you can't find it quickly enough). If you see a big explosion, you might want to note that this is a good target area, and redirect your efforts there until there are no more juicy explosions in the area, depending on your plans for other targets.

One good reason to build multiple Berthas is that if you take out a lot of power and the commander can't cloak anymore, and you spot him with, say a scout plane only for just an instant, your enemy may be overwhelmed with action and not realize what's happened. Bookmark the area if the screen fades before you can visually target the commander, and then let fly with multiple Bertha shots right where the commander is. You'd be suprised how often people just keep their commander in the same place after he's been scouted. Putting quite a few scout planes into the air just to spot the commander is always worth the effort; you can win the game literally in one or two shots, a matter of seconds.

Try to be a good judge of what will hurt your opponent most, and then kill it. I almost always go for fusions first and geothermals second, because power effects everything else in the game. And a commander standing by a fusion plant is just like Christmas.

Above is a great Bertha defense. You know as soon as you start attacking your opponent's base with your Bertha, he will do everything possible to take it out. That is why you can never have too many fortifications guarding your Bertha. The Guardians and Sentinels cover ground attacks, the missle towers cover fast air attacks (stealths, fighters, scouts), and the flakkers handle the slower air attacks (bombers, gunships). Also, it is a good idea to jam everything with at least two jammers, just in case one gets taken out. Also note the energy storage facilities. These may aid in the Bertha's firing speed if you do not have a high energy storage. This setup may seem a little extreme, but in many of the games I have played this just wasn't enough.