Just two time-saving and structured working tips for OS X:

How to set the preferred screenshot location while using the excellent built in screenshot utility of OS X (source)

1. Create the folder in which you want the screen captures to be saved in the location of your choice.
2. Open a Terminal window and type this:

   defaults write com.apple.screencapture location /Full/Path/To/Folder

3. Log out and log back in, and the change will have taken effect.

How to set the preferred location for pdf downloads when you actually choose to directly view it with Preview (source)

To redirect the PDF download to a specific location, launch Safari and open its Preferences panel, click on General, and set the ‘Save downloaded files to’ selection box to the spot where you’d like those PDFs to land.

Thanks to macosxhints.com!