Ok i have a basic understanding of theory but im using a capo on a song on the 3rd fret and the main chord is a G (but with the capo i believe its technically an A#) so i believe wherever i am is the key of the song and i want to write a little solo, what scale/key should i be using to make it sound good? cause i dont like the sound of the scale where im playin the chords and the only other place i know the scale is wayyyy to far down on the neck. any help would be appreciated
3 frets up from G is more likely Bb than A# (as that on has an ugly has collection of sharps while Bb major is just Bb and Eb)
ok its a Bb, what key/scales should i use though to make it sound good?
...uh, Bb?


Just do whatever you'd do for G Major, but move it up 3 frets.
"Virtually no one who is taught Relativity continues to read the Bible."

The key signature is not defined by where the capo is, but where the "resolution" note is (usually where you begin and/or end the piece). The capo just makes it easier to reach that by using the fingerings of open positions. The scale(s) you want to use kinda depends on the other notes of your progression. Gm would be the relative minor of Bb.
Since capoing at the third fret moves everything up a minor third, naturally the key of whatever your playing goes up a minor third as well. So use Bb.

You said that you were concerned with the "places" on the neck you know the scale on. A Bb major scale is Bb C D Eb F G A, not just 6-8-10 6-8-10 7-8. Thus, anywhere you can find one of those seven notes is a perfectly fine place to play. It's generally a better idea to use the key of the piece than a scale shape to write something. As we love to say here, scales are a collection of notes, not box shapes. It's fine to use box shapes as long as you know what's behind them. Also, phrasing is more important than just scales will ever be.