Hi!
I am a 4th year medic and tutor in the subjects mentioned-
What has already been mentioned is amazing advice- starting early gives you so much time towards exam season to revise rather than stay stuck studying. For geography, make your own notes- make sure you have all your case studies mastered. Read them out to people (or your mirror or stuffed toy)... when you reword something you have learnt it does wonders in retaining that knowledge!
Practice exam questions early on- they are so similar to the questions that come up in the real exam and you will know what type of knowledge you are expected to have!
Good luck!!