There are so many places to acquire fresh flowers. The first is a reputable flower seller or florist. The florist is a professional flower seller that deals with flower suppliers all over the world; they are familiar with acquiring large quantities and unique varieties if given proper notice. Florists are also able to sell you flowers by the stem or in cut flower arrangements suitable for home design.
In many large cities there are flower stands (San Francisco, New York) where a multitude of fresh flowers are displayed in buckets for you to select or pre-made bunches are available. These cities also have major flower markets that may be open to the public after certain hours, or on specific days.
The grocery store or mass market retailer also offer bunches of flowers. Many times they specialize in seasonal flowers that are arranged by variety or color, for example a bunch of all red tulips, or a bunch of pink lilies only.
Web-vendors or on-line merchants sell similar bunches of flowers that are pre-packaged and distributed directly from a flower importer. These flowers usually arrive dry-packed and need time and proper care to hydrate before designing. Farmers markets can offer an interesting collection of regional or seasonal blooms; many times these products can be organically grown. Farmers markets are popular meeting spots and the journey can be just as fun as the products.
The most important thing to consider is the reliability of your chosen flower seller. They should be well versed in availability, proper care and freshness. Develop a relationship with your specific flower seller, finding out when the best time is to buy specific varieties, proper care and handling, and availability.