For advanced mac users, you may get frustrated when you can't find a hidden file and have to access it through the terminal.  In OS X, there's an easy workaround to change the finder's default mode to always show hidden files.

Open the terminal and use this command:

defaults write com.apple.Finder AppleShowAllFiles YES

Now just restart the finder by holding down the option key and click and hold on the finder in the doc until the menu pops up. Now click "Relaunch" and all your hidden files will be shown in the finder!

Be careful when editing these files, make sure you know what you're doing when editing hidden/system files or you could mess stuff up for yourself. Always make sure you back up before making changes! To revert this command, just use the same command but change the "YES" to a "NO."

A useful reason for this might be editing the hosts file to block distracting, malicious, or just plain bad websites.