There are many players that are too afraid to lead away from a King, but when the auction tells you that your side needs tricks quickly you have to do it and always listen to the bidding.
NEVER lead (or underlead) an Ace against a suit contract. Against NT usually the 4th highest from your longest and strongest (unless you have 4 cards and a sequence to lead the top card from). Therefore against a NT contract, you will often lead away from an Ace or a King.