Whats better to SHARED or not

[doppler]

I plan to create a program using many SUB procedures.  Values to change in a sub must be passed or DIM shared.
But which way makes more sense or is more efficient?  Shared it all (variables), shared some variables ?

Questions like these is a big factor to size of program, speed of the program and forgetting to shared a value.
Common sense is out the windows when playing with QB64 code.

Thanks