Before you deadhead flowers around the garden, collect some seed from those that you like the look of. Note, though, that most hybrid plants will not "come true" from seed: this includes many showy annuals. But simple, cottage-garden types usually reproduce faithfully. Dry seed of annuals carefully by leaving it in a dish or envelope in a warm room for about a week. Then keep it fresh until next spring in a air-tight container in a cool place (the fridge is ideal). Seed of perennials can be sown immediately while it is still fresh. Keep seed trays outdoors in a shady, cool place and make sure the compost in them remains lightly moist.