I've found I really need a system to get things going. I just can't dig through bricks to find things while I create. It 'disturbs the flow'. I know everyone has their own good system that works for them. This one seems to work for me so I thought I'd share it.
I make these tags (above) which go on each tray. Images are from my LDraw program. Info is in sync with BrickLink so that I'm using the same language and IDs as them for repurchasing and research. Since I'm a graphic designer, I have access to page layout software to make this. I found with some experimenting that using large numbers for size worked best. Additionally, stacking the numbers rather than writing 2x4 for example makes for an easy visual scan across the shelving. A large color bar reinforces the correct color at a glance. In cases of non primary colors, I'll add a tag in lower right corner to help further specify the color. Special pieces requiring more information will have more info under the category description as seen in the headlight example above.
So far so good. The tray placement order is evolving as the collection expands but for now it seems to be netting out hierarchically at: color / brick - plate - slope - special / size. I'm very pleased with this system and find grabbing pieces I need so quick and intuitive, I hardly need to look up. (Though, I'll admit my collection is yet small. That will no doubt change when things grow larger.)