What is the best way to approach a problem to find the optimal solution in fast and efficient way?

There are many ways to approach a certain problem to find the optimal solution. I use the fish-bone methodology enhanced with a six-sigma approach to find the main causes of the problem, analyze them, see the different consequences of each cause and then come up with a set of solutions prioritized by the following criteria: Cost - Time - Return - Sustainability of solution.   

Firstly define the problem then formulate a hypothesis. Find analogical reasons and estimate its solution. Implement the solution.

Gauge the nature and effect of the problem; identify the source and people involved with it; initiate discussion with people concerned to seek their views on solution; analyse the options within the same group of people and have a mutual acceptance on the best solution with accountability and time span.

Monitor it closely and do the fine tuning if required.

Thereafter, make it a case study for others to learn from if they get into similar situation.