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Evaluating stocks to buy and sell can be a tricky business, even with all of the data available at your fingertips. Out of the dozens of ratios and metrics that give clues to the financial health of a company, a few of them are extremely useful for their simplicity and effectiveness.

Here are ten financial ratios that can tell you most of what you need to know when you’re scouring the market for good stocks to buy.

Price-Earnings Ratio (P/E): This number tells you how many years worth of profits you’re paying for a stock and you calculate it by dividing the stock price by earnings per share. All things equal, the lower the P/E the better. The most frequently used earnings number in the calculation is the total earnings per share over the past four reported quarters. You could also use “forward” earnings, which is the average of Wall Street ’s forecasts for the current fiscal year.

Benjamin Graham, the legendary investor investor and Warren Buffett ’s teacher at Columbia University. postulated that stocks should trade for a P/E multiple equal to 8.5 times earnings plus two times the growth rate of earnings.

Without some context, the P/E has limited value in finding cheap stocks. For the market as a whole, the S&P 500 currently trades for 19.47 times the past 12 months of reported earnings. The average P/E since 1935 is 15.86, suggesting the market is a bit pricey.

Some industries like homebuilders and commodity producers tend to trade at low P/E multiples because earnings tumble in a hurry so investors don’t want to pay too dearly. Rapidly growing companies like Netflix, with a P/E of 382, or Facebook, trading for 222 times earnings, are valued much more on the hope of future profits that bring the P/E down to something more modest.

For individual stocks, you should compare a stock’s P/E with those of its competitors. It’s also usually informative to compare the current P/E with the average multiple over the past three-, five- or even 10 years. If it’s lower than average, it’s a sign that you’ve spotted a possible bargain, but that all depends on growth, which leads us into the next ratio to watch, the PEG ratio.

New York Stock Exchange (Getty Images via @daylife)

Price/Earnings Growth (PEG) Ratio: The PEG ratio is another Benjamin Graham invention which attempts to measure the degree of a discount or premium you’re paying for growth. The calculation is to divide the P/E ratio by the long-term annualized percentage growth rate of earnings, ideally the next five years’ worth. A result of less than 1.0 implies that the market is not fully valuing the prospects for future growth.

The downside of the PEG ratio is that future growth rates are notoriously hard to predict. Companies’ growth profiles can change, sometimes drastically. Apple is a good example. It trades at a svelte 0.86 PEG ratio based on a P/E of 12.2 and a five-year EPS growth rate of 14.5% annualized. That’s appreciably lower than the 72% growth rate over the past five years, but still enough, if it materializes, to suggest that Apple buyers are getting a bargain.

Price-to-Sales (P/S). Similar to the P/E ratio, the price-sales ratio divides that market capitalization of a stock by total sales over the past 12 months, instead of earnings. Popularized by investment manager and longtime Forbes columnist, Ken Fisher, the price-sales ratio tells you how much you are paying for every dollar in annual sales.

Because there are times when cyclical companies have no earnings, the price-sales multiple can be a better indicator of a company’s relative value than the P/E. Like other ratios, you should compare the P/S of a stock of those with competitors and with historical sales multiples. Sales are also more difficult to manipulate than earnings, giving a more reliable gauge of value. Keep in mind, however, that the beauty of a low P/S ratio can be spoiled by a constant lack of profitability and large levels of debt.

Price/Cash Flow (P/CF): This useful measure of value is obtained by dividing the market value by operating cash flow over the prior 12 months. It strips out items like amortization and depreciation from earnings and focuses on cash generated by the business. This provides a better way than P/E for comparing valuations of companies from different countries that have different depreciation rules that can affect earnings.

Lower readings are preferable but keep in mind that there is more to cash flow than what comes from operations. Free cash flow is what’s left over after paying down debt, buying back stock and paying dividends. Negative free cash flow is forgivable as long it’s not a chronic problem, but companies that cannot produce positive cash flow from their core business operations can face eventual liquidity and solvency issues.

Price-To-Book Value (P/BV): This ratio tells you how much you’re paying for every dollar of assets owned by the company, and you calculate it by dividing the market capitalization by the difference between total assets and total liabilities. The idea is to approximate how much money you could put your hands on if you shut down the business and sold off everything. As with most price multiple metrics, price-to-book is best used by comparing present multiples to historical averages.