A/C doors
At my airline, our SOP is that you open door as soon as seatbelt sign is off. I understand that this can be dangerous but stems from the fact that we operate 2 different types of jet, one of which is the 146/rj .
This is one of the resons for the policy as at most airports their steps cannot be attatched untill the door has been opened fully, hence the reason for this policy. I imagine as they leave the fleet the policy may change.
I would like to point out that included in the sop is that a crew member has to be stationed at said open door at all times.