Answer: Flower gardening is lots of fun and very rewarding, it is also an ongoing learning experience -- getting familiar with the plants and the growing conditions and microclimate of your own space.
For a sunny location you might try marigolds, petunias, blue salvia, cosmos, cleome, gladiolus or zinnias. For a shady area you might try impatiens, begonias, or caladiums. These are all annuals and need to be replanted each year.
Some easy perennials for sun would include purple coneflower, coreopsis, sedum and daylilies (Hemerocallis). Some easy perennials for shade include hosta (many varieties available with different colors and patterns of foliage), ferns, and bleeding heart. These plants should live for several years -- or longer.
You will want to improve your soil prior to planting so as to give the plants the best chance to thrive. Add organic matter such as compost or old rotted leaves or well aged stable manure and bedding and loosen the soil down about a foot for perennials, eight inches for annuals. Plant your plants (or seed if you use that for some or all of your annuals) and water them deeply to settle the soil. Now add a layer of several inches of organic mulch such as shredded bark. Cover the soil around the plants and under them but do not allow it to touch the stems. The mulch will help keep the soil evenly moist and keep down weeds.
During the season, water as needed to keep the soil slightly moist but not sopping wet. Use your finger to check the soil and see if and when you need to water. Watering deeply less often is better than a daily light sprinkling, and watering at the roots is more efficient than using a sprinkler.
Since you are so new to gardening, you may want to look at a book or two. The Dummies series includes a book on annuals and a book on perennials. I think they give good, straight forward practical advice. Both of them explain about deciding whether you have shade or sun, preparing the soil, selecting and planting the plants, and then ongoing care. They shoudl be available in bookstores and most libraries.
Enjoy your new flower garden!
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