Jamie, To keep it simple, I try to only give 40 minutes of homework on any given night. I made up a "5 minute rule", 5 minutes per problem. That equates to 8 problems any given night. Bruce Mushet
I assign and grade homework nearly daily. In 6th grade, I try to keep it to 15-20 questions. Sometimes, with more involved problems like surface area, I keep it at 8-10. I assign problems from the problem sets provided in the text. I usually work selected odds during class and assign the evens. Obviously, some sections this doesn't work, and so I have to select them differently. I try to make sure that at least half of the assignment is the new material. Review is good, but it does no good if they didn't start to grasp the concept the first time.