Got a few more of those cheezy "how to paint" art books out of the library. Their silly, but there's always a couple of gems worth holding on to. Also just ran across the cheezy art magazine website has demo's. Things that caught my attention this time:
Do small (9"x16" max) studies with time limits (15, 30, 45 minute)
If you hold true to value, you can really experiment with color
Break your subject up into 2 tones (the lit part and the shaded part) and get those tones down first (probably the mid tone of each) then if you have more time you can get more detailed within those tones. (so a cueball would be flat white, with a flat crey crescent on the bottom)
try and get your shadow shapes to blog together for a more solid feeling whole (don't have a bunch of shadow shapes scattered all over if you can help it)
the strongest point of contrast will draw your eye, strongest dark vs light, or hardest edge, or both, so plan that in your composition if possible.
another limited palette suggestion: lamp black (for blue) yellow ochre & terra rosa