The little I've learned about landscaping I learned through trial and error. First, shorter plants need to go in front, and second, flowers are more effective when grouped, rather than scattered.
Here is a spectacular example of mass planting from a yard in Puget Sound. The bright bed of red-orange crocosmia is like the bull-fighter's cape calling for attention. It's captivating on its own, and stunning as a foreground to the water in the cove.
Although I'm land-locked, I have a lagoon-shaped area of lawn. A bolder border would refresh it.
What changes do you plan on making to your gardens?