^ I kinda agree. That's why I think one of the very first thing to know is the key of the song. If it's in E minor, for example, just bantai E minor pentatonic. It may not sound great all the time, but it never sounds "wrong".

Another tip is to ring out or emphasize a note that belongs to the chord currently being played, so you need to take into account chord progressions. For example, if the chord progression is Am G F and the key is Am, when the chord is Am, emphasize A, C, or E. When it's G, emphasize G, B, or D. When it's F, emphasize F, A, or C. It might sound a bit simple and predictable, but at least the notes are in perfect harmony. And that's what I did for my first solo for my own song, and it sounded quite nice.