QUOTE(Chopinzee @ Dec 18 2007, 07:25 PM)

Just try memorising a bar or two each day, and no more than that. Don't move on 'til you've got the last one.
. . .
when i do need to memorise something, then just a little bit each day, it seems to work.
This strikes a chord. Despite playing piano for more years than I care to remember (admittedly with some long gaps where I only did barely enough practice to ward off decline) I had very little memorized repertoire until I started to work at it seriously again, about a year ago. It seemed ridiculous that I could not play for anyone without planning in advance and taking a stack of sheet music wih me. Also, everywhere I looked the advice of top pianists was the same. If you want to play well, you must ply from memory. They might differ on other matters, but on this they agreed. And they are right. It is only when you play a piece from memory that you have sufficient attention free to listen to yourself and realise just how awful it all sounds!!
This is getting a bit off-topic, but what follows might be useful information.
Unfortunately I am no Argerich, capable of learning the entire Tchaikovsky Concerto No. 1 in two weeks. Like Chopinzee I too find that there is a (rather small) limit to how much I can learn each day of any one piece. It varies with the "density" of the music - a bar or two of a Bach 4-par fugue might be more than enough, but I might manage 10 bars a lighter textured sonata movement by Haydn or Mozart. (I am talking here of memorising the music - not mastering it technically and being able to play it with well-maintained steady tempo, properly shaped phrases etc. - i.e. making it into something that is less than excrutiating to listen to).
But although there seems to be quite a small limit to the amount I can take of any one piece in a day, I find that I can work in parellel on several different pieces, so long as they are clearly different in character and style. So, a Bach fugue, a fast movement of a Mozart sonata, a slow movement of a Beethoven sonata, a Chopin study, a Rachmaninov Prelude, a pice from Debussy's Children's Corner, and an arrangement of Ain't Misbehavin' can all progress nicely side by side.