Online or Mail Order
First and foremost, always buy organic. Mail order catalogs and online garden stores are becoming an increasingly popular way to stock up on seeds. The advantages are value and variety. Also, seeds can be ordered for the upcoming season as early as January and bought all at once, at a time when a lot of garden stores are either closed or running with minimal stock. I like Territorial Seed Company, Totally Tomatoes, and Seeds of Change. If you do buy early, store seeds in a cool, dark place to keep them fresh until planting. While fancy packaging and boutique seed companies are on the rise, it's all down to individual taste and trial and error – experimentation is half the fun.
Your Local Garden Store
As the season gets going, nothing beats a personal relationship with a good local shop. If you happen to have one near you, limited selection can be made up for in expert advice and a well-curated stock. Either way, the back of your seed packet provides most of the information you'll need to plant, including seed depth, soil temperature, days to germination, light requirements, and seed spacing.