So I'm trying to play George Strait's song "Run" for my girlfriend some time soon and I'm having trouble kind of jazzing the song up. I'm slightly past a beginner, I'd say intermediate in skill level.

What I'm having trouble with is coming up with some kind of solo/interlude riffs that would go along with the chord progression, which goes like G / A / Bm / A/C#...

I don't really know anything about musical theory (I don't even know what key the song is in, G's my guess since it's the first chord). So my question is, could any of you theorists or songwriters out there recommend a scale I could use to create something? Or perhaps even a few riffs I could use? I'll be playing it on my acoustic solo and singing..

I came up with a more appealing way of playing the chords, like this:


So, I need an instrumental part badly. The song sounds too dull with just my singing and even this I can only play on the verses with only a few notes to sing, I just strum on the regular ones. Suggestions, please! And if you could tab out what you mean that would be extra helpful too, cause I don't really understand anything that would qualify as musical jargon.

Thank you ultimate-guitar forum junkies! I know you will not let me down.