What advice would you give a novice pilot on controlling the rudder?
It's very normal for most students to struggle with the rudder initially. 

One aspect that got me while learning to fly: 

Unlike stick inputs is not 'applied pressure' that measures the effect of the rudder, but the actual physical displacement of the pedal. It was quite usual for me to feel the need for right rudder, increase pressure on the pedal but with very little actual pedal movement, so there was practically no effect on the a/c. 

So I made a conscious effort when right rudder was needed to apply pressure enough To Move The Pedal. 

In other words if you want to double the effect of the rudder you need to double the pedal displacement, not double the pressure applied.

Second thing that got me to using the rudder correctly:

Make a mental note to use rudder 


when using the ailerons 
when changing power settings. 


Pretty soon these actions will become linked by the brain and you will do it unconsciously. Then with time you will also learn to use the correct amount.

On feet stance

I am pretty short at 1.70m so I was usually selecting the closest setting for rudder which was placing the rudders very close to my knees, and as such it was difficult to properly use them (as my body was literally resting on the pedals). I was once advised to push them further back and it has made a world of difference: adjust them so that maximum deflection requires just a little bit of hip effort and almost a straight knee. Try a couple of positions and see which one works best; your instructor can help to show you the proper adjustment, and it does make a word of difference.