In Effective Grading: A Tool for Learning and Assessment (Walvoord and Anderson 2nd ed., 2010), the authors offer 13 strategies for "making grading more time-efficient." The list below summarizes and combines some of these strategies into a more compact set to help get you started.
1. Know where your time is going."
2. Invest time up front to save time later.
3. Let technology do some of the work.
4. Don't be the first or only person to assess the work.
5. Focus feedback on what students can use to learn.
Consider Text Expansion. You can set up a system of simple codes that create longer strings of text automatically as a kind of shorthand to let you provide feedback faster. You can combine the "minimal marking" technique (see #5, at left) with rubrics (#2, at left) and text expansion (below) to develop a powerful grading “combo!” See these articles from the ProfHacker Blog for more information: