I'm not sure if this is a good thing or not, but I don't give every assignment a grade. I will check as much as I can, or have the students go over the answers. But some assignments I do not assign points to. They usually don't know what is graded and what isn't until they get it back. That encourages them to do every assignment because they don't know what will be given points and what won't. The downside is that a student might miss only 1 assignment, but that assignment is graded and it affects their more than it should.
Whenever students turn in their HW packet incomplete, I send it back home with a notation "please complete and return with parent signature". The HW comes back within 3 days completed w/ a signature.
I do not grade each homework assignment, as this is not a "fair" grade. Some children have parents who help them, and some children do not. Each child's home life is different, therefore, I award a check mark for completion. At the end of the nine weeks I give a homework grade. It is worth 100 pts. I divide how many homework assignments I have given by 100 and for each missing assignment, that amount of points is deducted from the homework grade.