From D&D 3.5 to 5.0(5E) - 26 - Aid Another to Give Your Buddy an Attack Advantage

If you feel like your character can't roll high enough to hit this monster, but maybe the Paladin standing next to you can, then you can forgo your attack action in D&D 5.0 and instead choose to use the "Help" action to help the Paladin hit the monster on her attack.  Simply tell the DM that you are going to put your thumbs in your ears, wiggle your fingers in the direction of the monster while doing a little dance.  If the Paladin then choose to attack the monster before your next turn, the Paladin will have advantage on her first attack.