Few points keep in mind during buying a guitar

Always go with any experienced person (guitarist) while buying a guitar

Hand: If you are lefty, buy a left handed guitar and if you are righty then buy right handed guitar.

Body: Check for any deep defects and any scratches on guitar. See inside of the guitar and check, this is actually made up of fiber, rather than plywood. 

Fretboard: To check this first play the guitar if it makes any additional buzzing sounds besides the note, there is some problem in the guitar.

It should be absolutely straight and not make a bow (To check this see from the ends of the guitar) and there should be truss rod in the guitar if there is no truss rod, don’t buy that guitar.

Bridge: This bridge raises the strings above the sound board allowing to play them easily. The bridge should be symmetrical in height.

Tuning Pegs: Take help of seller or your friend to tune the guitar and play it if the guitar produce some ugly sound after short period of time that means there is some problem in the tuning pegs of the guitar so don’t buy it.