Give an extra safety talk to all personnel who does any type of maintenance.
You should stress things such as lock out, tag out, and where possible try out (to ensure the power is off; also ensure no one is around it and in a safe location before you try it).
Put that key in your pocket, so that no one else can use it to turn the power back on. If more than one person is performing the maintenance, each person should have their own lock and key. No one should share their key or allow someone else to go disconnect or reconnect the power (no matter how long of a walk it is). This is not a place to save time. Release any tension that may exist or any stored energy it may have.
You should stress the importance of blocking it from motion. Anticipate the different directions it could move and block all possible motion. Don’t forget to teach them “How To” block it from motion (don’t assume they know how).
Cover the normal things like, wearing PPE and following other safety procedures that apply to the job.
It is up to those performing the maintenance to take action.
Supervisors: Make extra checks on the workers to ensure they are locking, tagging, and blocking out. Correct those who you see behaving/working unsafe and reward those who are behaving/working safe.
Never assume they know how to do it the safe way. Teach them! To demonstrate they know how, have them teach you the safe way.