Sear Stephen

If you can start the preparation from 3rd semester like starting you need to understand basics of every subject and according to my prior experience, I can say that you will get most of the questions from  3rd year and 4th year too. So try to remember all the basics. Cover Maths and Aptitude in the 2nd year because you won't get maths in 3rd/4th and you will get plenty of time in the 2nd year. Try to use those time in the best possible way you can.

All the best.