Your main consideration when choosing the right bracket should be the mounting dimensions as dictated by the mounting holes on the back of the TV - you'll find this mentioned in the specs/description of the TV. Look for VESA 200x200, VESA 400x200, VESA 100x100, etc, etc - the numbers are actually the distances, in mm, between the mounting holes. Most large TV brackets are adjustable or manufactured to take the various sizes into account although some are single size (mainly the smaller TVs I think).
The weight of the TV is obviously another important factor to consider however modern LCD/LED TVs are very, very much lighter than they were even 4 years ago - my current LG 42" SMART TV (12 months old) in the living room only weighs about 25lbs whereas its predecessor, 37" LG LCD, weighs a massive 76lbs! (it's not wall hung I hasten to add). 4 wood screws into the studs of a wall will support a 25lb TV easily, very easily.
Another thing to consider is how close you want the TV to be to the wall - a lot of brackets are advertised as "Slimline" models which put the back of the telly to within an inch or so of the wall. Whilst this is lovely and takes full advantage of the thin design of modern TVs you have to consider how the connections for all your other paraphernalia come out of the back of the telly - some come directly out perpendicular to the TV (my LG has a couple like that) whilst other makes have overcome this issue by designing a kind of indented feature so that plugs/cables lie parallel to the surface of the casing.
Don't be fooled into buying expensive mounts - some manufacturers will try and rob you of a hundred quid or more but there is no need at all to shell out more than about 30 quid on Amazon .. you can even pick them up for about a tenner or so which means that if you pick one that you don't like it's not a huge waste of money when you get a another.
I currently use this bracket with my 42" LG mounted across a corner of the room. If needs be I can move/swivel the TV so that it is flat against the wall to make allowances for where I/we sit when watching it (i.e. family viewing, single person viewing) although it's not moved around too often:
http://www.amazon.co.uk/dp/B00VVCAG8C?psc=1
I've also got one of these -
http://www.amazon.co.uk/gp/product/B000RIXEVW?psc=1&redirect=true&ref_=oh_aui_detailpage_o09_s00 - which did put the TV very close to the wall but cabling issues and some glare coming in through the living room window forced me into buying the articulated one mentioned above.
The options are endless to be honest - you could be adventurous and go for something like this --
http://vivomounts.co.uk/black_ceiling_mount_vesa_bracket_led_lcd_tv.asp (good for a bedroom, maybe not a living room) or go really basic like this --
http://oldhousecrazy.com/2012/11/03/corner-mount-your-tv-on-the-wall-for-less-than-50-bucks-diy/
Good luck mate.
