Wow! What a great Post, Dewy!
I play the blues/minor pentatonic scale on a lot of stuff that's jammed around, I find it works well played over rock, blues, acoustic, ballads or almost anything thats being played... as long as you keep the 'feel' of the song in mind and 'follow the changes'.
I think the blues/minor pentatonic scale is a great start into improvisation... one moveable shape that shifts up and down the neck to suit your needs, nice n' easy to learn and use.
play at the 5th fret or 17th fret for Am/C, open or 12th fret for Em/G, or as Dewy mentioned 7th fret for Bm/D
Use this to get your fingers moving freely and to help with building riffs, and as a stepping stone to chord tone methods like
Planetalk - It's a nice ,easy starting place
