Here is what you need to do:

 1. Find two vertical studs, that is all you need TWO... 
 2. Get a nice rectangular piece of poplar or oak (maybe 2by2 or 2by3 depending on the size of the TV; the idea is to make this an anchor for the TV).
 3. Affix this piece of board to the studs with 3 inch nails or screws around the location where you intend to hang the TV.
 4. (optional) Paint this board to match the wall color.
 5. Once secured, you can bold the mounting hardware anywhere on this piece of board. 
 6. Secure the TV to mounting hardware.

If you have other items to mount such as BluRay, DVD player, Roku, etc. follow the steps below:

 1. Purchase a pack of "cable tie mounts" 
 2. Pack of thin zip tie (the idea is to place cable mount at the location where you plan to mount the device example, device is  4 by 4 inch, secure four cable mount 1 inch apart and 4 inch between in height)
 3. Run zip tie under those cable ties and secure device you wish to mount. 

Let me know if you need clarification on any of this.