My two are 10 and 14 and these STILL apply 
Don't wrap your brother in copper wire you borrowed from school and attempt to plug him into the mains. He is not Frankenstein's monster and it is NOT scientific.
Don't repeatedly slam yourself into lamp posts, it is NOT hug a lamp post day.
Don't steal your brother's comfort blanket and proceed to tell him a horrid story of how it was murdered and is now being buried under the street by the workmen around the corner as you speak.
Don't set up your brother's PC to have a screamer appear as soon as he moves the mouse.
Don't bite your sister and blame it on the ghosts.
Don't attempt to use your father's CDs he needs for work to practice your 'DJ scratching skills' with. Neither of us will be impressed.
Don't pour gravy in the toaster.
Pet hamsters who have passed on do NOT need a viking burial. They will be buried the old fashioned way.
Do NOT borrow your sister's makeup, doll yourself up as Heath Ledger's version of The Joker and hide under her bed until she lays down for the night. The resultant scream will bring several neighbours running to see what happened.