I use an A440 tuning fork for my A string then bring the rest of the guitarto that standard.I've been doing it that way for so many years that I getting better at doing it by ear alone.

I still have a problem with trying to sharpen the note.Sometimes I will play the A and it will sound flat.I bring it up to what I think sounds right then find I have to retune the other strings. At that point I break the tuning fork back out and find that the A string was spot on to begin with.

Oh well, back to the tuning board.

One thing that is nice is that my guitar stays in tune quite well. At festivals I can go campsite to campsite,pull it out of the case, and it will be in tune with the other instruments.

rr