I talked with a friend yesterday concerning how to prepare scores for band type music, and he told me a few things,

1. Treat the violin as a voice. What does a 2nd voice do?
2. Avoid hitting the melody when doing harmony.

Here is also an excerpt from our chat: 

Me: Is there any way to start working with a song scientifically?

Google....the 5 basic notes of modern melodies(He's talking about the pentatonic scale)

simple enough, I realized I played these notes when improvising, but didn't realize it
thanks for the reminder, I forgot these a long time ago 

stick to those notes and you can't go wrong...then try playing OFF of them.

Me:
okay. What do you suggest when all I have is a chordsheet? Is there some information I can get from the chordsheet+lyrics

you will usually play tonic scale or the 5th of the key that the song is played in
but try to diminish the 3rd, 5th and 7th in the scale to see what effects you can get

Me:
so for example C, I''ll be playing in A, and pentatonic for the riffs/improvs . Edim, Adim and Cdim for effects. Should I use arpeggios for the chord parts?

not necessary. When I play slide guitar, I use mainly single noted or 4ths

Me: (lol)

Okay, I can't wait to finish baking and try it out
Cake's still in the oven

go to youtube and listen to some dixieland while you are waiting for your cake
It will blow you away

Do you have certain artists in mind?

some of Louis Armstrong non comercial tunes might be kindergarden for you

I see what you mean by the 5th
I didn't realize that playing in a different key would sound good for 2nd voicing

very basic idea on harmonica

(5mins later...)
I just heard it. Some trills and echoes, right?

you'll get a better idea with this one
I gotta go work..Good luck

Any comments guys? 

Major Pentatonic Scale

1 2 3 5 6 1(or 8)
Minor Pentatonic Scale

1 b3 4 5 b7 1(or 8)