Nearly all LCD TV screens on the market use a 4 hole fixings system and a square formation, this is called the VESA Pattern (Video Electronic Standard Assoation).
The simplest way is to measure, or look up, the Interface Size of your screen, that is the horizontal and vertical distance between each of the four mounting screws on the rear of your TV. We would recommend you do this regardless of whether a bracket states it can accommodate your screen size or not, this type of description is only a guide. There are other points to consider when choosing a mount or deciding where to mount your TV screen.
Most modern LCD / LED screens have a wide viewing angle and do not always need to tilt to give the best view. Idealy the screen should be at the same level as your eyes. If you like to watch most TV upright in chair, then the screen would be ideal at around 1 meter from the ground, flat to the wall. If you like to recline in a chair then mount the screen higher and use a mount with a tilt.
With the weight of LCD / LED TV’s getting less and less they can be safely mounted on most walls. If you need to add support to your wall, fix some ply wood to the wall to spread the load.
When deciding which mount to use consider the positions of the AV sockets on the TV screen. If they are on the rear of the LCD TV, then you will not be able to access them without taking the TV down. If the screen is too close to the wall you may not be able to plug anything in.