I think that there are several ways of making sure that you have a successful peak season:
1. Decide on your rates and set them and your availability in your listings a year in advance, so that you get the people who like to prepare in advance. Also, some people want to make sure that they get the accommodation they want, and are prepared to pay more to make sure that they do, so this also an opportunity to try to put prices up a little (you can always bring them down later).
2. Make sure that you get any preparatory work (maintenance, improvements etc) done WELL in advance. There's nothing worse than frantically chasing suppliers and tradesmen just as your guests are about to arrive.
3. Try to find suggestions for ways to improve your offering, whether it's a welcome gift, smart new toiletries, or something else. Guests love feeling that you care, and that you've made an effort, and it's these things that they'll tell other people about.
4. Write to all of your old guests and tell them about what you're improving, invite them to come again etc. Even if they don't book, they'll be reminded of your property and may mention it to others.
5. If you have a website, Facebook page or Instagram account for your property, start posting enticing images and posts in the winter to get people interested!