HVAC Zone and next step Process Questions

[gripp2020]

Zones and AHU questions...

OK question concerning my learning process for HVAC in Revit.
1) When I am selecting spaces to be in a zone, how do i know how many spaces to add to that zone? (For example) What tells me that 4 spaces should be in this zone instead of 5? Is it my paragative?

2) Once that is done, how do i know what AHU unit to use for that zone? Is this information the ME would provide? 

3) Say for instance, if im hired to do the entire layout and IM expected to know this, where do I get this information from? I know that the Zone has a list of calculated air and actual air supply in the space, so is this what i use to determine the unit to use, dependent on how much calculated air the space needs vs the amount the unit pushes? 
PLEASE be as elementary as you wish, it WONT offend and DONT assume that i know what ever small steps you would think is too insignificant to describe!!

I just need to get a "PROCESS" down that i can kind of stick to when starting projects. I learn and retain things so much better when i know WHY something is the way it is.  

Also, as far as a process goes, once i lay out the zones, should i create another view and lay out the AHUs in a different floor plan view or turn the color/filter off and lay it all out on the same zone view?  

Thanks

[adam.jw]

This is what zones are SUPPOSED to be used for:

http://wikihelp.autodesk.com/Revit/enu/2013/Help/00001-Revit_He0/0328-Build_th328/0971-MEP_Mode971/1...

"Zone and spaces are independent components that are used together to achieve a common result.

• Zones: consist of one or more spaces that are controlled by equipment that maintains a common environment (temperature, humidity, and so on). You create zones to define spaces that have common environmental or design requirements. Spaces in unoccupied areas such as plenums can be added to zones. Spaces that are on different levels can be added to the same zone. You can create zone schedules and use a zone schedule to modify zones."

TO BE HONEST. I'm stilling trying to kick my mechanical team in the pants to use Revit for more design analysis. So currently, all we use zones for now are dumb groupings of spaces (Area A, Area B, Area C, etc of a multi-wing building).