I've been having a problem lately with my potstickers sticking to my pan too much. This didn't start happening until recently.   I'm using my stainless fry pan rather than a nonstick. Mostly, because I like this pan the most. But perhaps I'm just using the wrong tool for the job.  I've tried to let them cook longer after the water has evaporated even until some of the bottoms burned as an experiment. even then some still stuck.  Here is my current method.   Get pan hot over medium high heat. Add a couple tablespoons of olive oil. I've tried more and less with little change. Let oil heat to ripple. Add potstickers. Add .5 to .75 cups of water. cover and steam for about 10 minutes. Let dumplings fry for a minute or two.  
This trick made cooking in my stainless pan much more non-stick, including potstickers (or "mandu" in Korean^^)  Edit: That's unusual that the cooking instructions have you add water. I usually fry my frozen potstickers straight from the frozen state (perhaps they are pre-boiled?). You will have to use the BOIL/BROWN method to utilize the technique below.  Use the "water test" to know when the pan is hot enough to add oil. Besides being fascinating to watch, passing the water test ensures the pan becomes amazingly non-stick.  When the pan is hot enough, water will ball up like mercury and slide around the pan without evaporating. The temperature required is pretty high, but I've found the non-stick properties remain if I add the oil and let the pan cool to the cooking temperature I want.  Note: preheating the pan like this applies to non-stainless steel pans, but water only balls up like mercury on stainless steel.  Detailed explanation of how/why this works: On properly heating your pan 