What you need to do is visit gardens to get a sense of what your taste is. More than anything else, it is important to develop a visceral sense of what you like, and learn the whys later - because life is too short.
I'm a community gardener, but love to go to the major botanical gardens near me, and near you, the world class, New York Botanical Garden in the Bronx ( http://www.nybg.org/ ) , Wave Hill in Riverdale, NY ( http://www.wavehill.org/ ), the Brooklyn Botanical Garden (http://www.bbg.org/). There is much to be learned on how to arrange gardens with people in the work done under the aegis of Tessa Huxley at the Battery Park City Parks Conservancy ( http://www.bpcparks.org/bpcp/home/index.php ) and to walk into large manmade oases like the Olmstead and Vaux designed Central Park, Prospect Park, Clove Lake Park, Van Cortland Park, and their work throughout the United States and Canada - I'm in love with Olmstead's wonderful park on Mount Royal in Montreal.
But any garden, no matter how humble has much to teach you, if it is created with care and love. Your newspaper's horticultural pages, the local garden club, the ladies tours of garden clubs are essential to your education, as well as seeing the power of a community garden in the midst of a teeming slum, or in the center of a block covered with rubble.
And never ignore the gardener - the woman or man digging is always your friend, and a source of much real knowledge. And it is a good thing for you to volunteer with your local Parks Dept or help with a bag of dirt for a senior gardeners because while you're schlepping, you can glean pearls if you have the sense to listen and to ask a few, well chosen questions.
There are many books on gardening, and design, but first the manual, visceral, and learning to see, and developing taste - how the land flows, where to place that 1.99 rose bush from the discount store, and the thousand mistakes you will have to make have to be made. And looking at your work with a sore back, a can of beer, and knowing that while it ain't perfect, it sure is better than what was before. And then learning to appreciate what an amazing gardener God is.
Eventually you'll come down to West 58th Street to the Horticultural Society of the City of New York ( http://www.hsny.org/ ), learn who Gertude Jekyll was (http://www.gertrudejekyllgarden.co.uk/ ) , the significance of the Gardens at Versailles ( http://www.smithsonianmag.si.edu/journeys/01/jul01/feature_full_page_1.html ), make the acquaintance of E.B. White's wife, the infinitely more talented Katharine S. White of "Onward and Upward in the Garden" and other marvelous garden writers, and the stunning beauty of the traditional Japanese garden, (http://www.japan-guide.com/e/e2099.html ) and have your heart beat quickly in the deep of winter as you open up garden catalogues.
But first, friend - LOOK, then get your hands dirty, and realize that despite all of your unique gifts, it has all been done before, and well. Gardening, on your knees, is both a glorious and humble avocation - plan to get dirty and get your nose close to the dirt and worms - you'll see so much more.
Clinton Community Garden