Most of my songs are written out in a form of notation that some people call “Nashville Numbers“. Why would one do this? Because it allows you to play a song in any key without having to transpose or print off more copies of the song in different keys (if you can read the numbers and know those keys, that is).
It’s relatively simple. If you know the major scale and all the chords in a given key, then you can read and play Nashville Numbers. Each number represents a chord, and that number is also the root note of that chord in the major scale. For example, if we were going to play chords all the way through the major scale in C Major (CM), it would be CM, dm, em, FM, GM, am, b7, CM, which in Nashville Numbers would look like 1, 2, 3, 4, 5, 6, 7, 1.
For accidentals (notes that aren’t normally supposed to be in a given key) I like to add a sharp, flat, Major, or minor symbol before or after the chord number depending on it’s natural. For example, #5, b6, 2M, 5m, b5m, and so on. You can also denote different 7 chords just like lettered notation or add notes to the bass like usual. Like, 1/3, 5(M7), 1(aug7), 5(sus). Sometimes I’ll do 4 chords as well, so an F4 in the key of CM or something similar would look like 4(4).
Not all songs lend themselves to this kind of notation. When I do use it I try to remember to include the key of the song I end up playing it in and whether or not the guitar uses a capo. It takes a bit of practice but is immensely useful for worship bands. Have fun!
Here’s a cheatsheet from google images: