1. If you have a large space plant perennials. They come back the next year. My space was so large, there is no way I could fill it every spring. It was literally empty and is now full. Perennials spread and most come back with little effort.
2. Don't worry about where you plant things. As you learn you can always dig up the flower later and move it.
3. Digging up perennials and/or splitting them will not hurt them. In fact, they like it. Do not be afraid of the plant. Dig it up and get your shovel and split it. Now you have two plants...or three or four etc. And you can give some to your friends too.
4. You have to experiment. Sometimes you will plant a perennial and it won't come back, others will thrive.
5. Fill in your garden with annuals for more color.
Problems do come up and a big one is deer and rabbits eating your flowers. I have been told by many all the remedies for this (its kind of like when it is obvious you have poisen ivy and everyone walks up and tells you how to cure it). So what to do for deer: Rub soap on the trees, sprinkle cayenne pepper on your plants, get your son to pee around the flower beds, spray "deer fence" around your beds and on it goes. I have found the best thing, however, is to let my dog out when I see them. That seems to be the best trick. I welcome any other ideas.
Enjoy the sunshine...