"O mighty Laser Tower, we would like to obtain the Uber powers of Plasma Beams."
Wait, what? You already got a Laser Tower? That's great! This building is known to really pack a punch on weaker monsters and single-group monsters. It is useful to defend this tower with a Tesla nearby, as they can pick on loners easily. Laser towers only have little health, so make sure that you put an NECoRG in front of it. It's range is also too short to hit Daves with level 3 rockets, even at level 6. They're the best weapon against unbuffed pokey or fink bombs, as they have so little HP, they are killed in less then a second.
Laser Towers have a low range and attack a large number of monsters at the same time, just like Cannon Towers, but stronger. Attack them using Teratorn or D.A.V.E. with rockets level 2, so they won't take damage. They can be easily being destroyed by a level 3 or higher Champion.
Do not place a large number of monsters (like pokeys) near to a laser tower, because most of them will die on the first attack.
Also, fast monsters like Eyera and Bolt can outrun the laser when they are walking making the tower deal no damage. So, its good to use Eye-ras or Bolts to "annoy" the tower without getting any damage. Bolts are more likely to teleport without triggering the tower though.
Due to their splash damage properties, the damage Laser Towers should be maximized by funneling attacking monsters into groups. This can be done with excellent use of blocks to form walls and mazes to force attackers to path into the relatively short range of the tower. Another more unorthodox method is to use another tower as bait; attacking monsters will clump around the tower and after it is downed, the monsters are already ripe for Laser Towers and Booby Traps.
Always let a Sniper Tower or a Tesla Tower , or even a Aerial Defense Tower next to a Laser Tower, so it will be protected from distance atacks. The best way to use Laser Tower is to defend your yard from Dreadnaut Tribe's Brain attack. If you know the side of the yard where they will attack from, then place an empty resource harvester on that side. Place 2 Laser Towers in front of it. It's better to have at least level 4 laser towers. Click "I'm Ready Now" and see the brains come to the laser tower to be dead like flies coming towards a burning candle. It is also necessary to have other towers protect the Laser Towers because fast monsters like Eye-ra and Bolt can outrun the laser making the Laser Tower deal no damage.