When practicing a solo, mark phrases and sections, Isolate difficult parts and work each motive over and over. Do not think you can learn a piece by playing through and stopping where there is an error. When playing through a piece, go back to the problem spots and practice them. Next, connect the problem spots to the phrases around it. You now are sure that you have solved the problem.
The same process can be applied to memorizing a piece. Memorizing phrase by phrase using your ear, the “feel” of the part, and your intellect—internal vision of the page. Be sure that you have a mental vision of the beginning of each major section. Above all, practice with the music even when the piece is memorized. Memorize your music even if you plan to play from the part.