First, you need a monster with average/low attack and defense. (One you think your opponent could defeat.) Set a Waboku facedown, and Summon the weak monster. Your opponent will probably summon a monster and (if this is their first turn) let you go. Do not summon your level 5-6 monster yet.(you can summon other small monsters) This will lull the opponent into a false sense of security. When they attack, your monster activate Waboku. On your turn, Tribute the weak monster and Summon your Summoned Skull/Judge Man/Curse of Dragon, to attack the opponent completely off guard. Yeah, you could just summon the monster without using Waboku and waiting for the attack, but people usually prepare for that.