There are as many ways to do this as there are people, but they all revolve around seating the brushes properly. The method described above is one way of doing it. It is also a good idea to skim the comm after that, but not essential.
Another important job is to properly align the rotor in the magnetic field by correctly shimming it. TO do this you need to take the rotor out, take all the shims out, put the endbell back on and rotate the motor by hand one turn one way then release it. Measure the end play, pull the motor apart, add shims, put the motor back together, repeat untill you have 1.5mm toatl play and rotor is free to find its "free" position in the magnetic field.
You need to align the brush hoods too. Again there are many ways of doing it. I do it with a brush which I file flat and polish on the face that touches the comm. I stick this brush in one of the hoods, spin the motor by hand a few times, pull the brush out and measure if the wear mark (a little line) is down the middle of the brush. Move the hood acoordingly, until you get the mark perfectly down the middle. Repeat for the other brush. remive the mark off the brush by polishing the face lightly inbetween measurements to avoid confusing yourself.
Lube the bearings properly too.
Team Greasy Weasel
The best upgrade to any car is some driver skill.