What is the first thing you do after you get out of bed?

If not the bathroom?
Turn on the computer?

Best - unpack the guitar while the computer is booting up
and then go to the midi tuner -- 8notes.com Guitar Tuner
Select each string in turn to tune your guitar.
This guitar tuner uses MIDI which is a Yamaha product and precisely in tune too.

The pleasure of playing or singing in tune can never be underrated.

Google Search: playing "singing +in tune"

Singing in tune all a matter of practice and is inexorably linked to ear training. As one improves, so will the other
see iBreatheMusic Forums - Singing

You have to imagine the note in your head, if hear it inwardly first,
and it will just come out right!