How to tune a guitar without a tuner

Tuning by ear - it’s kind of one of those party tricks that’s bound to impress other musicians in the room, if you can do it accurately. Say you pick up a guitar in a music store to try and it’s slightly out of tune. Are you going to whip out your phone and load up a tuning app, or even worse ask the store clerk for a tuner? This would be a great instance where tuning the guitar by ear would be of great benefit to you, especially if you’re looking to try several guitars in the store. Or maybe [...]