How do you EXIT full screen mode in Yosemite?
Click the minimize/maximize button a second time or press Control-Command-F simultaneously. The button can be green or grey depending on how you have configured the appearance under the General pane of System Preferences.

To resize window, simply double-click window bar.

The best way to do this that I have found is to put the cursor in the upper left hand corner and wait a second. The green button reappears (you also get the top bar back in case you want to do other things than change the view.) and you can click on it to get back to normal view.