I had the theory that if you can sing it (in key), you can play it. More to the point, get the chords to come out of your mouth. Play a chord and try to match the note vocally. I did this by singing the open string notes first (E, A, D, G, B, E)....I'd sing > EEEEEEEEEE, AAAAAAAAA ....and so on. Even if you're not a singer, and I'm certainly not, I feel it helps engrain the note in your psyche.

Maybe I'm crazy but it help stick the note in my noggin.