A great resource in Blackboard is the ability to grade assessments with a rubric. A well done rubric can be a lifesaver in your online course. When you associate your rubric with your assignment you get the ability to not only give points according to your rubric but also add personal comments for your students to see. This can also help eliminate a lot of the gray area when grading. The interesting thing about rubrics though is that they are always a work in progress and it is usually not a one size fits all type of deal.
There are a lot of great online resources out there to help you develop your own rubric.
View this video to see an associated Blackboard rubric in action. *Note this video was orginally made for the RNBS Nursing Faculty