If “now” is right before you discuss an assignment in class:
Fantastic! Thinking in advance about your goals for the assignment and talking with students about those goals is a sure way to improve your grading experience later. First, you’ll want to sit for a minute and think about why you are assigning that project, paper, lab report, quiz, presentation, or what-have-you. Write your goals down. (Friendly advice: if your answer is “because I wrote papers in college, too,” you may want to think a little bit more. Let’s not do unto others just because it was done unto us!)
Once you have a clear sense of your goals for the assignment, and write those down, you will have an easier time grading student progress toward those goals. In other words, setting goals or establishing outcomes for your assignment liberates you from having to grade everything! So, for example, if this problem set is designed to help students practice a certain concept, you can and should only be grading for student progress on that concept. Think how much time you’ll save!