In short a successful marketing strategy is one that brings you in more business than what it costs you. Hence the importance to always be checking your ROI.
Jef Lippiatt , Owner at Startup Chucktown
I think Lisa is on point, but I wanted to add that focusing on your target audience (and knowing who they are) will help drive better results.
It is not only frustrating but unhelpful to try to target everybody. Focus relentlessly on the people or groups of people that already come to your business for your products and services.