It's never too early to start planning your garden. Knowing what growing zone you are in will help you know what you should be doing and when you should be doing it. You can find a few online guides to help you find out your zone (the Burpee website is one good source). The regional guide will help you determine how to map out your garden, how and when to start preparing your soil, how to lengthen your growing season and when to plant your flowers and/or vegetables in the ground.
While knowing your growing zone will help with developing a good timetable, you should also familiarize yourself with the type of soil you have to work with. Knowing the pH, nitrogen, phosphorous and potassium levels will help you correctly use fertilizers and other additives, such as lime, depending on the type of plants you want to grow. You can buy test kits with chemical drops and tubes at most garden supply shops, and you can even buy electronic soil testers; prices start at less than $10 and go up from there. Or you can locate your local agricultural extension office and pay for low- or no-cost soil tests (find your local office on the Department of Agriculture website for your state). In addition to learning about your soil composition, take some time to see how much direct and indirect sunlight your chosen gardening area gets during the day.
Make sure to check the texture of your soil as well. If the soil is hardened, clay and rocky, you might want to put in some raised beds. Raised beds are easy to make. You can buy prebuilt raised bed walls or make your own with used tires or recycled wooden barrels; just imagine a large, bottomless plant pot. Raised beds have walls to contain the dirt, a weed-barrier bottom and rich soil specific to the type of plants you want to produce. Another advantage of using raised beds is that they create automatic pathways between your plants, which will make tending and harvesting easier.
If you have not cleaned up last year's garden, or if you just need to clean out the wild vegetation, start preparing your planting area as soon as possible. Clean out old growth, weeds, rocks (especially if you are planting directly into the ground) and any other refuse. Use a rake to remove any winter mulch, as it can be a breeding ground for pests and plant-eating insects. Do not compost any weeds or last year's dead plants, as this can help to spread weed growth and disease from rotting vegetation.
Plan out where you will be planting flowers, vegetables or fruits, and if you did have previous gardens, do not plant the same type of plants in the same spots for continuous years. Changing plant locations will give the soil a chance to renourish itself. If you have a greenhouse for starter plants, be sure to clean it out with a mild disinfectant and allow the room to dry thoroughly before using it for this year's planting. Make sure your tools are clean and ready and you have a decent water supply and hose.
Armed with the knowledge of soil composition, space and sunlight, order seeds and plantable pots so you can start your plants indoors during the winter. You can directly sow the seeds into the outdoors if your season will be long and warm enough. Container gardens can be created in small spaces such as balconies and decks. Many seeds can be started indoors up to six weeks before the last frost. Seed packets often contain more seeds than you can use in a small home garden, but, luckily, some seeds can be stored for use the following year in tight, moisture-proof bottles when stored in a cool, shaded area.
While you are waiting to plant your starter seedlings in the ground, do some research about your plants. There are many wonderful books, magazines and YouTube videos with helpful gardening information. You can never know too much.