Every gardener has their favorite flowers that seem to make it into the garden each year, maybe in a different spot, worked into the design a bit differently than last year, but they are there. It is a little easier to have your favorites if your yard gets lots of sunlight every day.
Look at the vast selection of color when you shop for petunias. It is not just petunias; you can have your geraniums in just about any flower color you want, astilbe too. Interested in a theme garden of every white, red or orange flower, then you better take the big cart with you because you will have it completely filled with annuals and perennials to complete the garden.
If you have the challenge of shade gardening, choices are getting better each year. It used to be impatiens and coleus as the mainstays with not much change of flower or foliage colors. Now when you ask about shade gardening, the retailer will point you to the area covered by shade cloth and show you just how much has changed. Coleus now competes with hostas for variety of leaf color with hundreds of propagated varieties and more than two dozen seed varieties. Foliage ranges in serration, color variegation and the leaf size from less than a quarter to over several inches in length, like those you get with the "Kong" coleus series. Your favorite garden center retailer also will point out that there are now coleus plants that can grow in the sun, enabling you to extend your bed a little farther out the shade and into the sunlight. This gives the gardener additional choices in the yard where the sun-shade pattern is transitioning.
Perennials also have a place in most garden designs. Hosta, bleeding hearts and ferns for the shade; coneflower, Shasta daisy, mums and daylilies for the sun. These are just a few examples, as the choices are just about endless, just like the annuals. A big question from gardeners just starting out is 'Which ones do I pick that will grow and flower in my yard?' Besides the expert advice you get at the garden center, you cannot go wrong if you chose varieties named All-America Selections. These flowers are trialed all over the country and have to perform well in each of the trials before they are awarded this distinction. They are judged against other varieties of the same type considered to be the standard.
Quick reminder: You can buy the best of the best and still have a poor showing of blooms if the soil is not prepared to promote quick establishment. It all starts with the soil, soil amendments, and how and when we work the garden soil. Adding a good supply of organic matter is great start. Learn more at https://extension.illinois.edu/annuals/soil.cfm