* P/E (trailing or forward earnings)
* Enterprise value / EBITDA (trailing or forward)
* Enterprise value / revenue (trailing or forward)
If comparable companies trade at 15x next-twelve months earnings, and the company you're valuing is expected to earn $10M in the next year, you value the company at equity value of $150M.
Enterprise value = total debt of a company + total market value of equity - cash
EBITDA is Earnings before Interest, Taxes Depreciation and Amortization and is a proxy for a business' operating cash flow (as opposed to profits, which are not always the same as cash flows).