If you're not familiar with the Lean Startup, it's an excellent resource for any product designer. Eric Ries drills the concept of the "Build > Measure > Learn" cycle into your brain. He provides case study after case study of practical examples of folks who found success and failure along the way, and how the BML cycle helped them achieve ultimate success.
In the build phase, you build it quick. You utilize short sprints to get the work done. It doesn't have to be perfect (or even complete). You build enough to test your idea with a segment of people.
Then, you measure your successes and failures. This is the time to investigate what worked and what didn't.
Next, you learn from these findings. Seek to understand why things failed and why things succeeded. Not just the surface portions like interfaces, but the deep core services that are offered. Do you have the right market? Do we need to pivot? Where do we go from here?
Lastly, you start all over at the beginning to build. This is your chance to revise, continue to build it or ditch it altogether.
This invaluable process allows you to get to market in an efficient and timely way. I am so glad I spent the time to listen to the audio-book version of this book and have it enlighten my understanding of efficient product design.