It is a good idea to draw up a plan for your garden on paper. Look through magazines, shop the nursery aisles and look at other peoples gardens to get ideas for the types of flowers and plants you want to use.
Plants do not stay small so your plan should allow for growth. Planting several plants of one type or color does make a stronger impact. It is a good idea to buy at least three of the same plant.
A formal garden is one with regimented lines and strict rules. An informal garden is a bit more wild looking but still requires some careful planning. Most informal gardens only look like they just grew that way. Chances are, the gardener who created it spent a fair bit of time planning it out.
Start plants from seeds according to package directions. Lay out bedding plants when you are sure the weather allows. Many plants benefit from a little cold, but one killer frost can ruin any plants you have so carefully nurtured. Where you live will determine when you plant. If you are familiar with your surroundings you know how the climate will behave. If you are new to an area, it may not be a bad idea to check with neighbors or consult with a nursery.
Zone maps can be confusing. Many books and magazines provide planting guides based on zones but they are not always true. In Northern California for example, the winters are generally mild. Many plants grow through the winter and are that much stronger come spring. There are many plants not credited to the Northern California zone which do very well. For the most part, if a plant is well stocked at your local nursery, it will grow in your area.
Take into consideration how much sun your plot receives. Check the location of the sun on the garden during various times of the year. Most flowering plants and vegetables require full or part sun. If your plot is under trees or on the north side of a house or wall, you may not get enough sun for some plants.
Many people love a shade garden. There are many plants which thrive in shade. Bleeding heart, cyclamen, hosta, Japanese anemone and monkshood to name a few. Be sure that the plant you choose fits the site you intend to plant it in.