As a Brit and mentor, but not a teacher, I would advise as follows:
1) You should put the TV on a dry surface, away from sunlight.
2) You mustn't put too many plugs in one socket.
3) You must keep children away from the TV.
4) You shouldn't put water near the TV.
5) You shouldn't be/sit too close to the TV when you watching it.
6) You shouldn't try to fix the TV when it's plugged in.
6a) You should unplug the TV before trying to fix it.
Note that this avoids criticism (from some quarters) for ending a sentence with a preposition!
Hope this helps