An question about how to remove unused package from MacOSX turn out to be an example of "find" command:

http://forums.osxfaq.com/viewtopic.php?p=57887#57887
http://www.osxfaq.com/tips/unix-tricks/week98/tuesday.ws
http://javarevisited.blogspot.com/2011/03/10-find-command-in-unix-examples-basic.html

File Search tips in Linux - http://discuss.joelonsoftware.com/default.asp?pg=pgDiscussThread&ixDiscussTopicParent=18272&ixDiscussGroup=3

Another search tip, example of find base on time and size, and how to compare with other files - http://viralpatel.net/blogs/2010/02/some-useful-unix-file-finding-commands.html

Like search by name, depth, size - http://www.thegeekstuff.com/2009/03/15-practical-linux-find-command-examples/

use 'find' to delete branch of file: http://keithdevens.com/weblog/archive/2005/Jul/05/find.rm

By time - http://www.thegeekstuff.com/2009/06/15-practical-unix-linux-find-command-examples-part-2/

Use of empty - http://www.thegeekstuff.com/2010/03/find-empty-directories-and-files/

Find Anything You Need with fzf - https://medium.com/pragmatic-programmers/find-anything-you-need-with-fzf-the-linux-fuzzy-finder-tool-f48dfd0092b4