Both of these questions can be answered with the same question. If you do not have much experience, it might be hard to think of a good answer. Also, if your previous job was very simple or followed a regular routine, then a memorable accomplishment might be hard to think about. So take a lot of time to think of anything. Because answering this question with nothing to say is basically the only wrong answer. Here are some ideas. Did you save the company money? Did you create a new process and put it into place? Did you break a sales record? Did you meet a difficult deadline? You can use all of these types of experience for this answer.
These two examples are different. One is for a sales position and the second is for a technical engineer position. Both of them are great accomplishments. Sales is easy to answer because you can just throw out numbers and it sounds good. The second is a little more difficult because you have to explain the situation a little. But make sure you explain your scenario enough so the interviewer can see the significance of your contribution.