Remember everyone learns language differently.
Most people are visual learners, but others learn by listening or by doing, drawing or acting.
Revise what you have learnt in between language lessons.
Go over what was covered in your last class, and attempt to do any homework.
Practise and speak the new language as often as you can.>
Converse with fellow students or with the help of a language CD or video.
Learn from mistakes.
They are part and parcel of language learning, and without them you will not be able to improve.