Increase your vocabulary:
Read a lot, for example books, articles on the net, newspapers.
Use your English when you study other subjects (or when you want to find out more about things in your life outside school). Find facts on the internet for example.
Watch (and listen to) English speaking films/tv series with English subtitles.
Listen to music actively.
Improve your writing:
Always plan what you are going to write. Use key words, mind maps, lists, pictures or whatever you feel is good for you, but use something. Stick to the subject. See to it that you have a beginning that catches the reader's attention and a good ending.
Look up words that you don't know.
Try to vary your vocabulary. Don't always use the same words and expressions.
Always check your verbs. Keep a list of the irregular verbs close to you when you write.
Try to describe a lot, use feelings/colours/smells/movement,... in your text.
Use different perspectives
Answer questions like WHAT happened? WHEN? WHO did what? WHERE? WHY? HOW?
Write much about little, not little about much.
Learn and use linking words and expressions.
If you make mistakes, learn from them. If you spell a word in the wrong way, for example, write it in the correct way a couple of times.
Ask somebody to read what you have written and ask them for tips how you can improve.
Improve your listening:
Watch English speaking films with English subtitles.
Check out some listening exercises at my/this site.
Listen to music and really try to understand the lyrics.
Listen to news on the web (BBC for example)
Improve your speaking:
Always try to use English in the classroom.
Talk to your friends in English during breaks.
Play games on the net and talk to others online. (When you play with people in other countries of course.)
Improve your reading:
Check out some reading exercises at my/this site.
Read a lot, for example books, articles on the net, newspapers.
Use your English when you study other subjects (or when you want to find out more about things in your life outside school). Find facts on the internet for example.