Determining If You Have a Right or Left-Handed Guitar
The easiest way to tell if a guitar is right or left-handed is to look at the orientation of the strings.
As you look at the guitar face on, a right-handed guitar will have the thicker strings (low E, A, and D) on the left side of the fretboard, while a left-handed guitar will always have them on the right side.
The tuning machines, if inline, will move from the nut upwards.
Identifying Right and Left Tuning Machines
On Fender-style guitars, as well as a number of others, the tuning machines are usually mounted in a straight line along the headstock. These will require a set of ‘R’ tuning machines for a right-handed guitar or bass or a set of ‘L’ for a left-handed instrument.
Gibson, Epiphone, Gretsch, Rickenbacker, etc. style guitars and basses normally have three tuners per side (usually two on a bass) of the headstock, so you will need three ‘R’ tuners and three ‘L’ tuners for these types of guitars (or two each for basses).