I have recently updated my tutorial for nested arrays and formulas which was getting quite old. The tutorial is available here: Nested Families & Arrays
Just in summarisation though, best practices when creating parametric arrays:
1. Always use nested families for elements that are to be arrayed
2. Always constrain the two defining elements of the array in all 3 axis. (defining elements are either the first and second or first and last depending on which option you've selected when creating your array)
3. Always constrain your arrayed elements by dimensioning to their origins. (their origin is the intersection of the three "defines origin" reference planes - THIS SHOULD BE LOCATED AT A LOGICAL POINT THAT YOU WANT TO CONSTRAIN TO, TO AVOID EXCESSIVE DIMENSIONS AND PARAMETERS)
Hopefully this quick cheat sheet can be used to diagnose issues with malfunctioning arrays.