Most Macintosh users already know how to drag a folder that might be deeply nested over to the sidebar for quick access. This is a great way to speed up your filing process - just add your commonly accessed folders to the sidebar...the more the merrier...or is it?
OS X will automatically shrink the icon size of those items as more and more locations are added to the sidebar. Great news, except that the blue line which indicates the sidebar drop position becomes more and more elusive to find. Once or twice I have accidentally dropped a folder inside an existing sidebar item - and THAT is a recipe for a lost folder: "Where did my TPS Reports folder go!!?"
Solution: Select the folder which you intend to place in the sidebar, but instead of dragging it over, use this hotkey combination: Command + T. Done. It is instantly added to the sidebar...albeit at the bottom of the list. Don't worry though, repositioning is as easy as pie - no blue drop indicator line and no possibility of accidentally placing one item inside another.