The stackup is what controls the layers of a bare PCB; signal, power, ground, etc [1]. An engineer at your board supplier is likely involved in determining the stackup with the EE and PCB designer. The stackup and material selection of the bare board is one of the things that controls min/max trace width, proximity, etc. Once you have that info, you can plug it into your CAD tool of choice, for instance in Mentor Xpedition it's CES [2]. Makes things like differential pairs a lot easier.

1. http://blog.optimumdesign.com/hdi-layer-stackups-for-large-d...

2. https://www.mentor.com/pcb/xpedition/constraint-manager/