What is the most efficient way to evaluate a company?

Two important things

Accomplishments

Confidence by customers

The most efficient way to evaluate the company depends upon your controlling interest. As far as the evaluation of company to acquire it , the most efficient way to evaluate by Free cash flow Model using the Net present value technique using weighted average cost of capital as discount rate.

  

Efficiency of the method depends on the availability of data.. If you have market/comparable data available the market would be a quick approach... If you have business plan available for the business the DCF method would be a very good method to apply