Keyword research is the very basic and essential SEO activity and I prefer to spend a fair amount of time on it and apply different methods where possible. Of course number one source for me is Google AdWords, but I also look through Wordtracker's database, related searches from search engines, go for competition research and more.. I mean it really depends on how much time you have at your disposal, but the complex approach makes it possible to discovere real gems sometimes (although I am not saying it can be done faster). And, needless to say, I always check out number of searches, competition for every potential keyword and calculate keyword efficiency index. So, it may take you half an hour, as well as a couple days, but if you go not only for keyword research but for keyword analysis - half an hour will obviously not be enough.