I was taught one guide per foot for spinning and one per foot plus one for fly rods. On the fly rods this included the stripper. As a final perspective though Bass Bugs #4 is right on.

I use a formula given me years ago that I wrote a Visual Basic program to calculate the spacing for me. It calculates the proper distance to place the stripping guide and allows me to adjust distances to accommodate the ferrules. Once the guides are taped on based on this formula I still do the stress test and adjust accordingly to the bend/taper of the blank.

That's my system, everyone has their own. I find what is important is that you are happy with it once it is on the rod.