Search Amazon for books on the subject. Read the reviews. Buy the one that excites you the most.

I did that for guitar after fumbling with it for ~5 years. Within days of beginning "Fretboard Theory" I had the entire fretboard mapped and the foundations I needed for improvising engrained in my memory.

I'd imagine the Piano would be easier to start with too, since it's easier to thump keys than to produce any clean sounds on a guitar.