The secret lies in giving the artillery units a large sensor radius so that they can attack from safe distances, often times beyond the normal sensor range of the enemy fleet. The scout ship has the largest sensor radius among the ships, about equal to the sensor radius of stationary sensor arrays. Build a scout and send it toward your fleet of artillery. Do NOT group the scout with your artillery fleet. Instead, tell the scout to GUARD your artillery group. Normally, if you group the scout with your artillery and command the group to move or attack, the scout would move much farther ahead of the artillery ships due to its speed. When you instruct your group to attack, the scout would head straight into the enemy and quickly be destroyed by your own artillery fire. By instructing a scout to guard your group of artillery, it will follow the slow moving group at the same pace, staying in close with the pack. When you instruct your artillery to open fire, not only do you have clear sensor visibility of enemy ships some 10 grids away but the scout will also continue to stay in formation and not fly directly into the line of artillery fire. The result: artillery ships that can fire long distances, and see long distances.

Use Nebulas Wisely
Do not underestimate the importance of nebulas in Armada! Use them wisely; they work very nicely. There are countless strategies regarding how to can reverse the tide of the battle by using nebulas to your advantage. They make great war stories, like this one: On one multiplayer map, the key to victory was in the center of the map with 4 dilithium moons. The center, however, is completely enclosed by a ring of yellow nebulae, which kills your red shirt crewmembers. Early into the game when resources and tech was still low I sent a construction ship (500 crew) into the center. One of my opponents saw this and immediately sent in a fleet of scout and destroyer class ships (80 crew) to destroy my unguarded construction ship. Slow and without weapons, the construction ship reached the center only to take a pounding by these scouts. I quickly led my construction ship across the nebula ring, watching my opponent take the bait and follow. As soon as all his ships were across the nebula I went back. In his aggressive campaign to destroy my construction ship, he followed me. Each time we past the nebula, we lost crew but since the construction ship starts off with 500 crew and his Defiant-class only holds 80, I had a hidden advantage. After a few passes, my opponent's ships suddenly slowed to a sputter and began to drift. To the shock of my enemy, his ships were derelict while my construction ship was left standing! Not only was I able to build a starbase and take hold of the resources, but I was able to capture all of his derelict ships and use them for defense against any immediate low tech scout defiant attacks.

Always be mobile
Never put too much of your base in one spot or you can lose everything fast. The Klingon Subspace Ripple and the Romulan Phoenix can both destroy mass quantities of area in a split second. Also, keep a construction ship somewhere outside of the hot zones, that way just in case your main base is destroyed you can start a new base elsewhere. (Of course, its best to already have a small base set up elsewhere ahead of time just to be ready.

Recycle everything
Any ships you no longer use, or any buildings with no further use, decommission. Mining Facilities are at the top of the list, especially when you have limited moons. When spreading across a map, recycling Starbases can be a godsend. Use a Starbase to hold back forces, and when the coast is clear, decommission the Starbase so you have the Dilithium to build a new one elsewhere.

The Romulan Phoenix super weapon
The Romulan Phoenix super weapon is a thing of beauty, however the ship itself is very fragile and needs to be protected. What I like to do is send a couple of freighters in front of a Phoenix ship, that way when any other vessels or Starbases begin shooting at them, I can sneak the Phoenix ship just past enemy defenses, and watch them get obliterated by the resulting blast. Yeah, you lose freighters that way, but hearing the screams from your opponent is more than worth it.

The Borg Transwarp Gate is a 2-way street
When you find one popping up in your space, immediately send anything nearby to the wormhole through it, that way you get a great sneak attack at where ever they put their gate. Those Borg will get one very interesting surprise that way.