The text editor build into OpenSCAD is quite limited, you can't search for example. Luckyly it's really easy to use an external text editor.
Enable Design > Automatic Reload and Compile.
You can open the same file in a external text editor, when you save this document the preview is automatically updated in OpenSCAD.
When you use TextMate or Sublime editor you can add the following bundle to improve autocompletion.