1) check your grammar and spelling. Try not to make any mistake.
2) use your imagination and write something special and meaningful
3) you can learn more vocabulary, but sometimes simple word is enough.
4) write your composition according to the title. For example, if the title is *My favourite singer*, then just write the singer, do not write your favourite actor or book.
5) Read more English books and news. This can help you to write better English.