There are a number of tips that might help you write your essay:
1. Read good exemplar essays to get a feel for what examiners are after.
2. Choose your title wisely. You only need to choose one of the ten titles; select the title that you are interested in and have something to say about it.
3. Make a plan so you can have an argument or narrative that runs through your essay.
4. Send a draft of your essay to your teacher so they can give you feedback on the first draft. Then re-write the essay.
5. Remember to include footnotes and a bibliography set out formally.
In order to get your A grade for TOK you need to put time and effort. Enjoy the process; talk to people about your ideas and keep writing ideas down as you think of them. Good luck!