Do you know how to do all types of parking?
Make sure you read the "Guide to the driving test" booklet that you should have gotten when you got your L's or you can find it at the registry.
Go with at least one lesson with a driving instructor and ask him if he thinks your ready. Just be careful that they say that you need a few more lessons and they keep asking for money from you. I only went for two instructor lessons, rest was self taught.
Make sure your logbook is completely signed. Read through the driving goals, which are very helpful for driving in general and becoming a safe driver.
If you are a safe driver, then you will do well. Also, you need to be calm and composed, as if you are normally driving with your parents or something.
Common mistakes are generally instant fail items. These can be found in the guide as mentioned above.
Good Luck!!!