When I first started playing guitar as a child then as a teenager, there was really only one way to tune up: with pitch pipes. I had some really cheap ones that looked like this:
Of course, things are much easier now that digital tuners are cheap and easily accessible. I tend to use one on my mobile phone, but there are lots of options, including ones that you clip to the head stock of your guitar. With those ones, you can put your guitar perfectly in tune even in a loud environment (mobile phones and other ‘microphone-based’ guitar tuners pick up noises all around and so it can be difficult to use them unless you’re somewhere very quiet).
Whatever type you go for, you should always choose a ‘chromatic’ tuner. This means that it will tune an instrument to any of the 12 available pitches: A, Bb, B, C, C#, D, Eb, E, F, F#, G, or Ab. And, obviously, you will need to know which pitch to tune each string to. Standard guitar tuning is:
E – A – D – G – B – E
This is from the thickest (lowest pitch) string to the thinnest (highest pitch) and people often use acronyms to remember this order. The one I like the most is:
Eddie Ate Dynamite, Good – Bye Eddie
There are a number of other very common ways to tune a guitar, and you will see these marked at the top or beginning of any TAB notation. These include:
D – A – D – G – B – E
D – A – D – F# – A – D
D – A – D – F – A – D
And, if you wish to simply tune your guitar up or down in key whilst retaining the original relative tuning, just think of the notes of the chromatic scale:
Down 1 semitone (step) = D# – G# – C# – F# – A# – D#
Note that guitar tuners usually display the black notes on a piano as sharps (#) rather than flats (b). But, each have two names – this is called enharmonic equivalence.
C# = Db
D# = Eb
F# = Gb
G# = Ab
A# = Bb