My advice for year7's is to not get on the bad side of a teacher. If you do you can get in trouble easier and they'll always keep an eye out for you.
If you want to get good marks on exams, listen in class and take notes of everything, it will make it easier when you study. Intermediate is really close to high school and you will have many hard times, don't give up on things that are hard, keep trying.
Try everything but if you have something you really enjoy work on it and you will get better and better at it. For me if I work on something that I like and something that I dont like, the thing that I like seems to improve more. Don't compare yourself to other students just have your own goal. Also in class don't mess around or talk to your friends, that's for morning tea and lunch times.
Don't be scared to ask and answer questions, don't be scared to think that the answer's wrong. I have made that mistake a billion times, after your teacher tells you the answer you always think 'I should've put my hand up cause I knew the answer.'