The trick to getting a high score in Sprinkle is to use only the bare minimum amount of water necessary to get the job done.
If one fire's above another, think about taking the highest one out first so that the spill-off can start getting to work on the one beneath. Use common sense, save water for high score.
When pushing boulders up hills, you may need to adjust the angle of your nozzle as it moves along the curved climb.
Ice blocks only need a very small amount of water spray to get them sliding.
Ice blocks can also be forced under water, so if something above them is blocking movement, consider bobbing them underneath it.
Always duck when your fire-truck starts moving.
Try shooting your waterjets at the little fireflies that are littered around some of the levels for bonus points.
If you see an exclamation mark over a burning building, switch your firefighting attention to that hut immediately or the hut will burn down completely, ending your level attempt.
If your vehicle has started moving when a hut burns down, you won't fail the level, but you will have a penalty applied to your final score.