This seems more like an organizational tip, and it is that, but it also saves money. At night, while you are cleaning up the dinner dishes, pots, and pans, dish up the leftovers into a tupperware (or pyrex dish, if you are concerned about BPA leaching into your food in the microwave like I am -- sue me, I'm a little freaky about these things) and stick it in the fridge. The next morning it is ready for you to grab and go.
I cannot tell you how much money this has saved us; the wonderful combination of Baboo's thriftiness and slight to moderate culinary laziness means he prefers leftovers for lunches, and if they are ready to go he will happily grab them out of the fridge and eat them.
Similarly, if you can't bear the thought of two or three bucks per kid for school lunches but find the thought of packing lunches in the morning even more intolerable, make them the night before and stow them in the fridge. In the morning, plop them in the backpacks before they head out the door. Again, this has, quite literally, saved my sanity with five children. I might be exhausted when I drop into bed at night, but by golly, at least lunches are packed!!!