Simply so, how do I get more relief on my guitar?
Threading both ends allows the truss rod to increase or decrease neck relief before running out of adjustment. Adjusting the threads on the end of a truss rod counteracts the tension of the strings and will increase or decrease the distance between the strings and the frets depending on which way you turn it.
Just so, how do I know if my guitar neck needs adjusting? If there is more distance between the string and the tenth fret than the thickness of a medium guitar pick, the neck will need to be tightened. If there is less distance or no distance between the string and the neck, then the neck will be need to be loosened.
Beside above, how do you know if you need a truss rod adjustment?
If you hear buzzing, or if the fret fails to sound a note, then your guitar neck has bowed upward toward the strings. This means that you need to loosen the truss rod.
Should guitar neck be perfectly straight?
Guitar necks are supposed to be as straight as the guitar can handle, however, not every guitar is capable of having a straight neck without intonation issues, fret buzz, or unwanted noises. A straight neck is in between a convex (too much relief) and a concave curve (backbow).
Should I tighten or loosen the truss rod?
Remember in a single action truss rod: tightening the rod (turning clockwise) straightens the neck, loosening (turning anti-clockwise) permits it to bow. Before you adjust the nut, make a mark on it that corresponds to a fixed point below it on the access channel to the nut.
Why do I get fret buzz?
There you have it. Three common causes for fret buzz: (1) uneven frets (2) excessively low string action, and (3) a back bowed neck. Just one of these problems is enough to cause fret buzz, but often times a guitar has a combination of these three problems all at once.