Pocket square, hence the word SQUARE! Your pocket square should be neat, fold the fabric into a SQUARE! It shouldn’t look like a clown napkin, like you pushed it down into the pocket and slowly pulled it out so it could collapse on your chest.
Generally speaking, your tie should JUST reach the waistband of your trousers, or slightly shorter, if you can’t take your jacket off because your tie looks like your borrow your son’s tie. You have a problem!
Sleeve cuffs should be exposed about half an inch, the arms of your suit jacket shouldn't be so long, a person would think you were hiding a jail ankle bracelet (I made that one up but you grasp my analogy. lol).