A few things I would write if I were making a howto for newbies:
1) A basic guide to theory
-Scales
-Chords
-Time sigs
2) Audio Resources
- Where to find free stuff (my personal favorite)
- Where to find low-priced good stuff (another favorite)
- Top-of-the-line equipment
3) Basic composition
- Melody
- Harmony
- Bass
- Playing techniques for instruments (such as legato, staccato, portamento, arpeggio, whatever ends in the letter o)
4) Drums
- this section would be reserved for discussion of drum types, like bass drums, snares, hi hats, cymbals, and their applications. I separated it from #3 because I think this needs its own section
5) Song Aspects
- Texture
- Dynamics
- Unity
- Variation
- Beginning and End
- Whatever else I missed
6) Specific help
- For acoustic music
- For electronic music
7) External links
- Basically I would use this section to link to helpful audio resources, such as:
musictheory.net
soundtempest.net
kvraudio.com
Just to name a few.
BTW, I wrote this on the fly, so don't expect it to be a good template for a manual.