A.W.
you have lots of good advice. What worked 3/4 of the time was telling my daughter what she could do instead of no. Instead of saying "no standing on the chair" we would just say "sit down please" or "bottom on the chair please". You seem to repeat everything a million times, but eventually they get it. I know how frustrating it can be but eventually they will outgrown that phase of outlets and cords and move onto something bigger and better! LOL
I still say NO too, but I really try hard to be conscience of when and how I say it.
best of luck.