Hi,
It depends on the interviewer.
1) What I generally observed during the interview was:
"What are the major challenges you faced in your payroll projects?"
Then the questions will be asked based on your response of the above question.
So, please collect some challenges you faced in your projects and make a logical sequence in that and explain it clearly. (Again, the challenges should impress the interviewer).
Please chose the challenges which are based on solving problems using SAP STANDARD functionality rather than CUSTOM developments. Most companies don't want to go for custom developments, and they want you to prove how best you configured SAP using standard functionality.
2) Of course, some interviewer may ask name of the config tables. If you don't remember, you can very well tell the IMG path for the same. They basically want to test you how much you deeply worked.
Please go through latest SAP threads/docs in SAP SCN and try to understand. Also try to answer, if you know. This will improve your knowledge & confidence.
Best of luck.
regards,
Bala.