This is a complex question, anyone trying to answer this will most likely give you a generic approach.
1. list priorities/goals
2. list of resources (financial/creative/tools/labor force,etc)
3. evaluate your non customers persona
4. evaluate your current customer person
5. cross reference with your substitute competitor and look for similarities
6. then focus on the differences and based on your goals (after being prioritized https://www.linkedin.com/pulse/what-beehag-humberto-valle-mba-lrea-sam?trk=mp-author-card) create marketing objectives that align with current customers, non customers, differences between brands and align them with your market.

A strategy or plan is not something that can be thought up without insight in your business.
As far as knowing if is working, well that is part of the strategy and objectives you have set in motion to be achieved. If you have short term goals you should be able to quantify or gauge yourself whether there has been improvement in work, employee, satisfaction, sales, profits, extensions - whatever your goal is.
Hire a marketing consultant for this and together build a plan that can be easily implemented and is cohesive with your goals, brand and resources.
You can give me a call or google me and consider hiring me as well as I have been doing this type of work for many businesses already.