Fancy search techniques on Google are all very well, but there are many occasions when a subject-specific site with targeted content will produce more relevant results.
Where do you find out about such sites? One way is to visit somewhere where they are listed, nicely arranged by subject category. RBA’s page on Business Information on the Internet is one example. Not all the sites listed are free to use, but the combination of free and fee might give you an idea of at what level the buck stops (or starts) when trying to access information for no charge.
Another way is to look at site reviews. Information World Review’s Pronetuser is well worth investigating, offering articles on major web resources and news on recent developments.
Put variety into your searching!