But to really dig down into the valuation of a stock you'll want to understand some key financial ratios to compare the health of a company with its peers, its industry and itself over time.

For example, let's say you want to value a high-growth stock. You would pick three businesses in the same industry growing at similar rates and find their average P/S ratio. Multiply that number ...

Some common methods of valuing private companies include comparing valuation ratios, discounted cash flow (DCF) analysis, net tangible assets, internal rate of return (IRR), and many others.