Just make sure that you don't feel there are any sections of your year 10 content that you don't feel comfortable with, as you'll be building on this in year 11. Also try and refresh any year 10 work over the summer as it'll make it a lot easier when you come back and revise it for mocks. Seneca Learning or Quizlet quizzes can be good for this...
And if you have any English texts you know you'll be studying next year, may be worth reading them over the summer if you have time. Will give you a good headstart!