Never follow a rule blindly. Always understand its purpose and put in the numbers to evaluate its cost/benefit for your specific design.
0. Always use the longest rise time you can.
Strategy: Keep the instantaneous impedance the signal sees constant throughout its entire path.
Use controlled-impedance traces.
Ideally, all signals should use the low-voltage planes as their reference planes.
If different voltage planes are used as signal references, there should be tight coupling between them. Do so by using the thinnest dielectric you can afford and multiple, low-inductance decoupling capacitors between the different voltage ...