Grading Homework

How should I grade homework? I can't get over the idea of not grading homework completely for accuracy, but I know that if I keep grading every question my life if going to end and I will not be able to grow as a teacher.

I don't want to not grade all of it because I don't want to give my students the impression that I don't look at their work, or that if they do set up a problem wrong I want them to get the feedback necessary to grow as a student. My cooperating teacher grades for completion of the assignment and then samples a few questions. Do you think this is a good way to go? Are there other alternatives for grading paper homework? I don't have the option to use an online homework system unless it is something I can do for free.