Types of Tuners
When tuning your guitar you can always opt to use a tuning fork that is in the pitch of (A) at 440 Hz, commonly referred to as A440, which is standard tuning. If you choose to use a guitar tuner, then just as with metronomes, functionality and user friendliness are vitally important.
Tuners have the ability to register/detect the particular note being played and will subsequently indicate whether the note is flat, sharp, or perfectly in tune. There are metronomes that actually have the A440 pitch setting on the dial/keypad. Many tuners have audible pitch settings for all six and seven strings.
When considering buying a tuner, it is a really good idea for you to buy an A440 tuning fork before you actually go out and buy your tuner, because you can use your tuning fork to make sure that the tuner you are thinking about buying has been properly calibrated.
Pay close attention to the needle/indicator light as you tighten or loosen the strings to make sure that it ends up being right in the center, and when it does your guitar will be perfectly in tune. Between the preceding function and the audible pitch indicator function, you should soon be able to distinguish when you are in or out of tune.
Any company can make a tuner that is absolutely fantastic, and the same applies in reverse where any company can make a tuner that ends up not really being all that great once you get it home. Some lower priced tuners may be okay, but more times than not the better tuners will be the ones that are at a higher price point.