I tend to grade for the big picture, rather than each little step. More points are given for having the right idea. Doing calcs right but having the big idea wrong is usually not worth much at all. Students start at 100% and lose points for errors they make, or for wrong answers. I do give partial credit, mainly for people who have the right idea, but the wrong calculations. No partial credit if the other way around. I like to design a test so the average is in the low to mid 70's. If it's not I do curve, and I don't wait until the end of the course to do it; I do it on each exam as I go along, so that the average matches the one I've decided on originally. That way students always know where they stand and can hold themselves accountable to that. I announce the grade cutoffs on my syllabus (90, 80, 70, 60 percent for A, B, C, D, respectively.)