Not as short answer: I don't, at least, not directly.
In my previous post, I mentioned that the primary problem with grades is the misalignment of the purpose of assignments (what you were supposed to learn) and the grade it receives (what you actually learned). The question of how to grade homework should come down to purpose. There are many reasons for homework but usually it falls into one of three categories:
- To preview future learning
- To practice current skills
- To deepen subject matter knowledge
None of these should affect your final grade in the class.
Number 2 is probably the most common and I'm going to throw it out right away. Clearly you shouldn't be graded for practice. I don't shoot 100 free throws in practice and then get credit for it in a game.
Number 1 and number 3 are a little different. In standards-based grading, the grade represents level of mastery in certain standards or topics. Your ability to complete homework should not show up in your grade directly, however it will show up in your mastery of the content. If you don't read the passage in the book or do the science experiment at home, you will lose out on an opportunity to improve your mastery. Similarly, if I don't shoot my free throws in practice I don't get punished. But I am also less likely to make them when it really matters.
What I actually do:
Anytime I assign homework I write it down in my gradebook. When it's turned in, I mark it completed. That's it. I report to the students their completion percentage every few weeks but it does not affect the grade. However, I make it as clear as possible that the homework is there to help them learn. I assign homework individually based on their needs and every few weeks I throw up a bar graph that shows the relationship in the class between grades and work completion. Eventually, most of the students see that the homework/classwork is not there just to get points. They stop asking about it. The homework/classwork is there to help them learn. That's it. As an added bonus, copying drops to almost zero because they realize they're not getting credit just for turning something in. Once students move away from points and percentages and towards levels of mastery, they begin to lose those "doing school" habits and focus just on the learning.