Some teachers have a very different system from me-they essentially tell the students none of their grades throughout the semester, nor how they actually calculate the final grade. They instead rely on vague subjective kinds of things like "improvement" or "effort." Students in Korea at least don't seem to mind this, bizarrely and I think it might actually help those teachers get good student evaluations because probably even the worst students might believe that they could actually get an A+ in the class, despite not really being able to actually write in a writing class, or converse in a conversation class. And the students who believe they're getting an A+ in your class will give you the best evaluations.
I, however, veer towards the opposite end of the spectrum. I spell everything out to the students in terms of how I will calculate grades on day 1 and then I review it at the end of the semester before final exams. I return all work to the students in a timely manner (less than a week) and let students look at their midterm exams. I use this system for the following reasons:
1. It eliminates the possibility of playing favorites, which I think is really unprofessional.
2. Students equate effort, studying and actually knowing the material with getting a good grade. Most classes with a foreign teacher up to the time they get me have involved, "Oh, just try your best," and "Communication is most important, don't worry about everything else." I set my standards far higher than that and expect students to live up to them. By the time they are 3rd or 4th year English major students at a mid-top ranked university in Korea, it's time that they have gotten a solid grasp on things like the past tense and use of the various future tenses.
3. I can defend any grade I have given to any student to the admin if required. With cold, hard numbers.
4. And finally, I get almost no frantic emails from students asking about their grades. They have put 2 and 2 together themselves and can't really argue with me.
Do you want to work at a Korean University? Check out: How to Get a University Job in South Korea: The English Teaching Job of Your Dreams