What Are The Best Practices for Low EMF Wiring in a Building?

There are really several issues here: 
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1- Avoid code violations which produce net current, see Karl Riley's book or his YouTube video: (this may be the most important one) 

2- Route the wiring away from or around the living spaces, rather than through them. 

3- Orient the Romex so that the narrow edge faces the living space. (Note that the field around Romex is not uniform. It is highest on the flat sides and lowest on the narrow sides. Twisting the Romex is only better than having the flat side towards the living space as it simply alternates flat side then narrow side towards living space. It is NOT better than having the narrow side consistently towards the living space.) 

4- Use metal clad (BX or metal conduit), to shield electric field if you must, but this makes controlling the flat side very difficult. A better solution is to enclose the Romex in grounded Aluminum Tape to shield electric field. 

5- A better option is to enclose Romex in grounded Magnetic Shielding Foil (for straight runs) and SpiraShield (for curved sections) to shield both electric field and magnetic field. Of course, this only works if there is no net current (see #1 above).

Source bottom of: http://lessemf.com/wiring.html

6.  I would also check sleep area and high usage areas for excessive electric fields to mitigate.  Ungrounded appliances, laptops, ceiling lights come to mind.