if it's a typein domain, setup a PPC search page on it to track how much it makes per day/week month. Or think to yourself, what would someone be typing it in be looking for, if it's something to buy, how much is that client worth? When you are looking to buy a name, domain investors I've seen pay as little as 1-2 years the typein value or upto 10 years if bought strictly for typein income. If you are SELLING a name, then you usually get the lower end of the market (1-2 years).

Other things are how easy is it to remember, etc.