There are many ways to tune a cigar box guitar. It all depends on the sound you're looking for as well as the string gauge you are using on your CBG. For example: .09 (extra light) strings are best for open A tuning: AEa (the lower case 'a' indicates and octave above the capital 'A').
Low – Middle – Middle (Low G, Middle D, Middle G)
Low-Middle-High (Low G, Middle D, High G)
Low-High-High (Low G, High D, High G)
Middle-High-High (Middle G, High D, High G)
Basically, there are 5 potential strings that are needed to achieve these 4 tunings. They are:
Low G
Middle D
Middle G
High D
High G
If you think of a standard 6-string guitar, or if you want to use a standard guitar string pack to do these tunings, you can think of it like this:
Low G – take the low A string (second biggest wound string) and tune it down a full step to G.
Middle D – this is the same as the D string on a standard guitar – third biggest wound string.
Middle G – this is the same as the middle G string on a standard guitar – the smallest of the wound strings
High D – the easiest way to get this is to tune the High E string (the smallest, unwound string) down a full step to D. You could also crank the unwound B string up two full steps (which would put it in the break zone).
High G – For this one you’d need to take a lighter-gauge high E string and crank it up two full steps to G.
3 String
Known as G5 Tuning, only two tones, but three strings
Tones 1/5/1:
String 5 (A) tune down to G / String 4 (D) / String 3 (G) or
A full G chord
Tones 1/3/5: String 3 (G) / String 2 (B) / String 1 (E) tune down to D
4 String
Tones 5/1/3/5:
String 4 (D) / String 3 (G) / String 2 (B) / String 1 (E) tune down to D or
Tones 1/5/1/3
String 5 (A) tune down (G) / String 4 (D) / String 3 (G) / String 2 (B) or
Tones 1/5/1/5
String 5 (A) tune down to (G) / String 4 (D) / String 3 (G) / String 1 (E) tune down to (D)
5 String
Standard bluegrass banjo tuning (use banjo strings)
Tones 1/5/1/3/5: gDGbd
6 string
Tones 5/1/5/1/3/5 Open G Tuning DGDGBD