Getting A* is not hard at all.
Attend classes. If you have a problem ask your teacher, watch online lessons ( Khan academy is a savior ), ask your friends for help. Honestly thats it.
I have AAA* and I studied for like 2 months in my entire A level. And most of it was dedicated towards chemistry. As long as youre enjoying what youre learning I think its easy. One thing I always found helpful is looking out for what my friends or people on the internet faced problems in. Tutoring others always helps you as well!
Good luck.