5th fret tuning trick!
The notes at 5th fret can be used to check the tuning of your instrument, providing you know the first note is an E.
Very handy trick if you suspect that your guitar might have gone out of tune and want to check quickly! N.B. The only note that isnt at 5th fret is the B, which is at 4th simply because of how a guitar is tuned.
Guitar Tuner Notes
You can use this video to check your guitar sounds right! It is a recording of each string played one at a time thickest to thinnest.