This is how I mounted my three, 23"inch computer monitors onto my wall. Using only some simple brackets and a piece of timber.
Step 1: Attaching the backing plates to the monitors
Step 2: Placing the brackets
In Australia our studs are 600mm apart, so my piece of timber is 1400mm long, so that i can screw it into the studs and have extra.
Step 3: Arranging the mounts
When you have got the position right, mark the mounts location so that you can screw it into place perfectly.
Step 4: Screwing brackets to wood
Step 5: Attach to wall
Cut off any excess timber that you don't require from the ends.
Locate your studs in your wall.
Using a level mark out the placement and height of your mounts.
Pre drill holes in the stud, so the screw will thread better.
Attach the backing plate to the wall with heavy duty screws.