I'm playing in a Dirty Country/Outlaw Blues band at the moment. These are the things I have learned along the way:
- Root 5 is king! You can get through a whole night tic tac'ing on Root-5 (well, you'll be boring as bats$%t but you will make it).
- follow the kick for your rhythm. If it's 'boom tic boom tic', you can play 'R . 5 .', if it's 'boom tic ba-boom tic' then you can just play 'R . R-R .' or you can play 'R . R-5 5'.
- walkups and downs are great embellishments as you change chords. Use scale walkups and downs rather than chromatic ones for true country, chromatic walkups work well for country blues.
- passing notes as you change chords are great, but again use mainly scale tones or dominant 7th as passing tones, not semitones.
- blues scale and your basic pentatonics are good scales to use for filling in or jamming.
- use short staccato notes if the drummer is using a closed hi hat, longer notes if the drummer is using open hat or other cymbals. Hopefully the band will be following, but if the rest of the band is chopping their comping chords, then you should use staccato as well.
- learn a couple of pentatonic, or classic country endings for songs.
All these are your emergency rules of the road for country type songs to get you going. Once you hear what the others are playing you can start to mess round a lot more, but keep it very, very simple in rhythm - play round more with the pitch you play instead of the number of notes.
Check my profile for a link to the band I'm in and a couple of tunes - I have been told they are pretty typical alt country type songs.