Rebuilding for Dummies

We're trying to lay down some sort of best practice for our PDM team members and would like to set criteria for file rebuilds.

I'd like to crystallise answers to the following three questions if anyone can help...

1. How do I know when to perform a rebuild on a Solidworks part and/or drawing file ?

2. When an a Solidworks part and/or drawing file is changed within a multi level Enterprise PDM  bom structure, how do I know which parent Sub-assys / Assys -  and /or drawings require rebuilds 

3. Once identified, how do I establish the sequence in which Solidworks files are rebuilt  within a multi level bill of materials.

I get the feeling we are doing this activity by gut instinct at the moment - but would like to know the science behind it all.

Any clarification would be appreciated.

SolidworksBill Of Materials