How to set up a QM/MM-Ewald calculation

Given any molecular system (from a dimer to a protein), what is the protocol one must follow to set up a reliable QM/MM-Ewald calculation?

Specifically, how do we choose the best parameters to control the Ewald summation in the $forceman section?

alpha 0.35 0.1
box_length 15.00
dielectric 88.0
ewald_scf_thresh_on 0.0001

This is discussed in the manual and in our papers: