Tips - How to add Developer Tab in Excel 200X/201X

Excel 2007

Office Button --> Excel Option button at the bottom
Excel Option window --> Popular button at the left;
Under Top Option for Working with Excel, check the Show Developer tab in the Ribbon option.

Excel 2010 and 2013 Ribbon

File tab --> Options at the left --> Excel Option window;
Click Customize Ribbon at the left -->  Main Tabs  --> Check the Developer item --> Ok