Well the last 2 are not transformers but I thought they were interesting. A couple of post back I included some info on transmission line transformers. Looking at these equivalent circuits you see a capacitor bypassing the circuit. In the bifiliar or trifiliar wound transformer this coupling will be more prominent because of the wires being twisted. In the binocular transformer the one caution is to keep the windings tight to emphasis the coupling. One other thing to take note of is the turns ratio Z transformation is not as simple as most make it out to be, not a direct N1/N2 relation.
In the text he emphasizes using low Z circuits.
I put one end in a vice and the other end in a low speed drill and run the drill until I get a nice twist then give it a couple of tugs to 'set' the twist in the wire. If you release it without the tugs the wire will try to tie itself in knots.