With so many choices and styles out there it is hard to know where to begin. I would suggest considering the following things to help with your choice. The color of your house and trim, style of architecture, your favorite colors, whether you want annuals, perennials, or flowering shrubs, and the longevity of your various choices.
If you have a colonial style house you can go with a more formal and symmetrical choice; Arts and Crafts Style a more cottagey, random mix would complement; Contemporary would be blocks of color, simple in design; Tudor style a more full blown English garden, etc. Using clues from your style of architecture will greatly enhance your home’s curb appeal.
As far as color is concerned, aside from the obvious choice of choosing a color that is nice with your exterior field and trim house colors, make sure to pick colors that you love, after all it will welcome you home each time you return. It’s amazing how different your house can look with monochromatic, complementary or contrasting color schemes. I like to play with my color schemes, and alternate these from year to year for a change.
This year in my front garden I have a monochromatic scheme with all pink annuals. I like to use annuals in front so that I can easily change schemes from season to season. You can provide accents by using several types of flowers in the same color, also providing texture as well, or varying shades of the same color which can provide depth. In my back garden it is all about contrasting colors — yellows, purples, oranges come and go with perennials blooming throughout the spring, summer and fall.
I like to treat the greenery with the same approach, and layer in various shades of green, textures, variegated leaves, heights, etc. It helps to show off the beauty of each when you highlight the differences between them and, it creates a lot of interest to the background.
My last tip for today is to add a little bit of yellow to every garden. Yellow makes every color look brighter. Even if it is just the yellow eye of a daisy, just a touch is all it takes. I learned that tip long ago from a fellow shopper at a garden center, and consider it one of the best tips ever; it makes a huge difference.