Here are some things sarah-marie notices when grading work:

Layout:
show your work (and I do mean all of your work)
no raggedy edges
use decent paper—reused paper, i.e. printer/copier output, is encouraged
if you have more than one page, staple
leave space between problems, and don’t do problems side-by-side
write legibly, or word-process if you can’t write legibly
don’t do your homework in red pen (or any difficult-to-read color)

Style:
use completely correct grammar
restate or recap the problem you’re discussing
make sure you answer every question asked.