I haven't learned it yet, but you'll have to look at the colors for correct orientation.
From what I can see: If you use the RUD E-perm, you are in the correct orientation if the FU sticker does NOT match LUF and RUF stickers. You are in the wrong orientation if they do match.
Bob Burton has great notes on this (see example below) with more angles so you should quickly transition to one look recognition http://www.cubewhiz.com/pllrecognition.php