Bring the garden in- to your refrigerator. Save the seeds from your favorite plants this year to grow next year, storing them in sealed plastic bags in your refrigerator. Don't deadhead your plants after they are done blooming. Instead, let them form their seedheads or seedpods and then collect and label them. Store in a cool, dark, dry place.
If you are saving seeds that birds like, such as sunflower seeds, place a paper bag over the seedheads as they dry.Hybrids will not be true to seed, but can be fun to play around with. You can really cut down on your gardening costs by starting with heirloom seeds that you save year to year. Who know- maybe you will cultivate your very own plant breed! Check out organizations such as the Seeds Savers Exchange. You can get an annual membership for around $30 and trade seeds with other gardeners. They can be reached by phone at  382-5990, or by mail at:
Seed Savers Exchange
3076 North Winn Road
Decorah, IA 52101
Some seeds just won't seem to sprout on their own without help. I've noticed this with many of the basils I grow. They are easily rooted from cuttings, so I rarely bother gathering seeds from them. Otherseeds must be soaked and dried before they are useful. Tomatoes are in the category. Just take the seeds out of the tomato and float in water. Then dry and store them.
If you don't have room to store seeds inside, then at least ensure the next round of plants by scattering seeds from you favorite plants in your garden. I have a chipmunk in my garden that likes to take one bite out of a tomato and leave the rest. That's ok- I let the tomato lie right where it is, seeds and all. Next year, I'll have volunteer plants in the same place, that will be hardier than anything I can start inside. I've let my pansies go to seed and now have two generations going. One set blooms in spring, sets seed and dies. By fall, the seeds have grown into small plants. Some of the parent plants bloom again in fall, along with a few of the baby plants. Dill and parsley are the same way - I always have some growing and some blooming at all times.
Don't forget that many plants are heavy reseeders and will do the work for you! Of course, they may not pop up where you want them, but you can always move them later. I like to ensure the process of reseeding by manually reseeding (scattering) a desired plant in a desired area. Great plants that reseed themselves include: nigella, sunflowers, cosmos, sweet alyssum, dill, cornflowers, parsely, yarrow, voilets and pansies
Can't bring the garden in, but want to save it for next year? Here are a few more strategies:
Try mulching heavily with leaves and grass. For very large, tender plants, you can fill trash bags with leaves and surround the plants with the bags, or even use hay bales/blocks to shield and insulate the plants. I heard of one gardener in North Carolina who protected his banana plant in his front yard by surrounding the plant with bags and bags of leaves.
For colder climates, it might be wiser to start off with the plant in a pot on casters, that can be moved in and out. Wheeling it in for the winter is not such a big deal if the plant is mobile. Then you can have your banana plant wherever you live!
These can extend the season and protect your plants. The best book I have read on the subject of season extension and plant protection is "The Four Season Harvest" by Elliot Coleman. The book contains diagrams and instructions for everything. There are tons of very unique and innovative ideas in here as well.
There are so many ways to bring your garden inside. If you plan ahead, you can have enough indoor plants and material to create a private paradise, decorate for the winter, and fill gift baskets for Christmas. Get creative, and don't be afraid to try new things. You can do it!