Above cabinet LED light placement
This is a matter of personal preference, however that being said you should avoid direct line of sight with the strip. 

For example, if you can see the LED strip while walking down stairs then it would be better to adjust the strip as to avoid this if possible as they are pretty intense on the eyes.  

An easy to make wooden lighting rail that basically looks like a triangle would direct the light up on the wall which has a nice effect and also keeps the light away from the eyes.