Two which work for me:
-Read the news and hope to find some newly hyped up topic
-immediately jot down on paper what you'd type in to search for that online
-add .com to the end of those phrases/keywords, and register those domains
-drop any which don't get any traffic within the first 24 hours and get a refund (its called domain tasting)

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-Monitor droplists for domains expiring
-Check the internet archive for a cached copy of the site to see if you can determine how big it was
-Check search engines for the domain to further investigate how popular it was
-Grab it the minute it expires, and park it.


Frankly I've been making more money putting up simple blogs with adsense, or recreating the original sites which people let expire than putting up a parked page....