Depends on kind of business, profit level and size.
A small (sub $1m in annual revenue) services company will typically sell on some multiple of "seller discretionary earnings" - basically; how much cash can the owner operator take out in a year (including their own salary). A "typical" multiple would be 2-4x SDE.
A larger services company will typically sell on some multiple of EBITDA (earnings before interest, taxes, depreciation and amortization). The main way this differs from the above is that the owners/CEO salary is not included. Traditionally the multiples here has been 4-6x EBITDA (which is what a "value oriented" private equity fund will seek to pay), but recently there is so much dry powder in the private equity world that those multiple has been pushed up, particularly for technology companies. 6-10x is not unheard of, more is possible.
A product or software (especially SaaS) company might sell on a multiple of gross revenue instead of earnings. Depending on how profitable the company is, this may or may not be a higher value than the above EBITDA multiple. Above a certain size, I would expect a SaaS company to sell for at least 3-4x revenue, more if growth is strong, even more for larger businesses.
In general you'll see multiples go up for a) strategic fits for larger acquirers (eg they can sell your product to their existing customers) b) growth and c) larger revenue companies.
This latter point might be confusing - why would a larger company not only get a higher price because the earnings/revenue is higher, but also get a higher multiple of that revenue? This "multiple expansion" occurs because there are (lots) more available capital to buy larger companies. Smaller companies are riskier and also the transaction and other costs (operating, optimizing) are similar for a $100m vs a $10m deal. There is also more leverage available at better terms for buyers of large companies.