Some whitelgihter rules:
Whitelighters have staff meetings with mandatory attendance
They are not supposed to eat on the job
Charges call take precedent
Whitelighters were not allowed to have any relationship with their charges 
but Patty and Sam as well as Piper and Leo broke this rule

Whitelighters can only be killed by the poisoned arrow shot by Darklighters
Killing a whitelighter gives the power to orb up to 

Whitelighters are led by the Elders.
Elders can be any age, their powers are mental, not physical
When Elders are retiring. they pass on their powers to a new Elder.  

Whitelighters can be sensed by the Elders when they use their powers. 
The only other way to find them is a blood relative