When the new semester starts, I always ask the students who their previous teacher was. And I write it down on my attendance sheet. As the semester goes on, I hear more and more little tidbits about what the previous teacher did, or didn't do. Like they never spoke English in class, or did some crazy thing for the test.
Something that I'm finding out immediately on the first day is whether the previous teacher did the mandatory online homework thing. We were supposed to do online homework that corresponded to our textbook and make it worth 20% (or more) of the student's final grade. Pearson Longman has a whole system set up to use with "Top Notch" or "North Star" that is quite easy to use.
As I pull up the website to remind students to sign-up, I ask, "Did you do this last year?" "No!" is the response I keep getting. Which I find shocking. My uni made it mandatory and some teachers just didn't do it.
My general rule about life at my uni (and perhaps why I'm still here 5 years later) is to follow the rules. As with any job, if you follow the rules, you can probably keep your job. If you don't, well, not so much. The secret to success in working at a Korean uni!