In grading papers and exams, first off make a key - alot points (or marks) to what parts of the question you want, i.e 1 point for this, 2 points for this, etc. Then grade each question separately. All of the papers, question 1 (or 1 and 2 if they're on the same page), all of the papers, question 2, and so on. Top to bottom, bottom to top. This should make you somewhat consistent. Also, you'll be able to see where student's go wrong and be able to deduce very quickly where each papers' problem has error (if any).
Although very time consuming, I find this helps speed up the process.