Basically, each German lesson your teacher should be giving you knew vocab to learn, and you should learn it on the day you got it because if you don't, and I speak out of experience, then you will certainly find it difficult when it comes to revision. However, when I revised for german I used the language programs on the internet and since my grandmother is German, that helped me a lot to. Basically, just try your best and if you keep at it and consistantly learn the vocab then it shouldn't be too difficult. I ended up with an A* but that was due to har work and determination. Good Luck and keep revising regulary!