Whats 10?? You mean the 10th fret? Ok I can tell your way off from where you should be. I'll answer what I think your looking at, but my advice is to search different topics in the music theory section of this site. But anyways the best roots to start at is the root (or key) of the song or the root of the chord you are soloing over. Like if the key of the song is E minor, then the best place to start as a root is E. If the chord is an E minor chord then the best places to start are E, G, or B. You can start on any note but the most commonly used are notes that exist within the chord you are playing over. Now for scales, you just match the root of the scale with the key of the song or the root of the chord (depending on how your using it). The scale that you choose should be relative to the key signature or the structure of the chord. If the song is in E minor, you could use the scales, E minor, E harmonic minor, or E melodic minor. There are many others, but the logic behind them is very extensive so I suggest serching the theory site. You'll definitely find more info there. Now to do it over a chord the scale must contain the same notes that exist in the chord. Take an E minor chord and the E minor scale. Both contain the notes E, G, and B so they are compatable. That should get you started.