As a Master Food Preserver, I advocate preserving food at every opportunity. I'm referring to canning, pickling, dehydrating, and freezing as your primary options. Rather than waiting to see what you have left over before you think about preserving, I suggest you plan some of your garden activities with preservation in mind. Grow to preserve.
I grow four specific crops with food preservation as my primary goal. My wife and daughter love my pickled green beans (that's not news to loyal followers; see my blog: "Your Garden in a Pickle") so I plant an entire bed of green beans devoted to a tasty end in the pickle jar. I'll continue that tradition this year and expand it by planting a new variety of purple-striped green beans. We may eat a few of the beans after harvest, but the large majority will be pickled.
There are varieties of cucumber that are bred specifically for pickling and I grow them. They taste good when eaten fresh, but they taste better when pickled along with some of the dill in my herb garden. I also add some of the garlic and hot peppers that I grow, for a little extra zing in each crunchy bite. Homemade pickles are a wonderful thing.
There are other plants in my garden that I grow for the preservation option too. When I harvest the raspberries, it seems that few make it to the house; they're too delectable to pass up. Those that make it to the kitchen are eaten by the handful, added to yogurt, or sprinkled on ice cream and other desserts, but in banner harvest years there are enough left over to freeze for future desserts or to make into raspberry jam. The same holds true for my blackberries and strawberries.
My fruit trees serve a dual purpose too. The apples, apricots, plums, and cherries are grown to enjoy fresh, but when they produce enough fruit they end up in the pickle or jam jar. Yes, I mentioned pickles when talking about fruit. Pickled apples, pear, and peaches are very tasty.
I also have to add herbs to this list. While I pick fresh herbs for use in the kitchen, I always harvest every last leaf before bitter cold hits. After drying the herbs, they're available in the kitchen throughout the winter until fresh ones appear in the spring.
What do you grow that could or should be preserved? Everything I've mentioned is easily preserved. How about carrots, cauliflower, broccoli, and zucchini? They can be pickled individually or together, especially at the end of the season when you have small amounts of each. I've also pickled jalapeno and banana peppers.
Try planting a variety of bean that can be dried and stored; I'm doing that this year. When you have leftover pumpkins after Halloween, cut and freeze the flesh for pumpkin pie, soup, or ice cream. When you have bushels of zucchini and no one left to unload them on, freeze them for making bread or stew. Think about planting similar squash plants specifically to freeze and use later.
Too much garden produce ends up unused. Too few gardeners preserve, donate, or compost their extra harvest. When you plant your first seed or potted plant with a specific use in mind, you're helping to eliminate waste. I support planting a row for the hungry. I encourage you to compost everything that can be composted. Food preservation is another option that should be part of your planning.