Work on your spelling. Go through your work and try to identify spellings you get wrong frequently. For example, you may get confused with ‘their’ and ‘there’ or get plural spellings wrong. Log on to www.ldonline.org/article/6192 for a range of strategies to help you learn spellings you find difficult. Practise.
Work on your punctuation. Again, go through your work and identify any errors that have been highlighted by your teacher. Common errors include using too many commas and not enough full stops; forgetting to use apostrophes to show possession or missing letters; using semi-colons incorrectly; putting apostrophes in random places wherever there’s an s, and forgetting to put the titles of poems/plays/stories in ‘inverted commas’. Practise.
Work on your vocabulary. Again, go through your work and see if you can identify words you tend to use all the time. Use a thesaurus to find alternatives or synonyms of these words. Practise using them in your work. Practise.
Read things. Try to find a good example of whatever it is you are writing. If it’s an essay, find a good essay. If it’s a leaflet, or a letter, or a magazine article, find a good leaflet, letter or magazine article. Try to look at a few of each. You should start to see words and phrases that are used frequently. Copy these down and learn them. Next time you have to write whatever-it-is, try to use them. Practise.
Don’t use more words than you need to! The best way to do this is to practise summarising texts. Read a magazine article that’s around 500 words and try to summarise it in 100. Or an article of 750 words in 200, and so on. This will force you to become more selective in both your reading, and your writing. Practise.