Usually, in upper pitchers, the tendril is behind the pitcher, while in lower pitchers, the tendril is in front or to the side. There are exceptions, though. Also, the upper pitchers often don't have any wings, and often aren't as colorful as the lower pitchers. All Nepenthes AFAIK can make them, but plants like N. rajah don't seem to in cultivation, because the stem tends to die before they are produced.
The only way that a plant will make upper pitchers is if the plant is vining. Along the vine is where upper pitchers are made. Lower pitchers are made on the rosette towards the ground. Sometimes, I think, if a cutting is made from a vine making these upper pitchers, that cutting will too make upper pitchers.
-Ben