Borrowing my buddy's guitar to try out before buying. I put new strings on it (first time doing it on an electric so I may have fucked up somehow). I can't get the intonation right on the first couple of frets. This mainly applies to the two thickest strings. The first string has pretty decent intonation. On the sixth string, the G is very sharp, while the 12th fret is almost in tune. I'm buying an action gauge, and a strobe tuner. I want to learn how to fix this kind of problem. Any suggestions on how I should proceed?