I try to knock them out

In D&D 5e, you can declare any damage as non-lethal, knocking an enemy out instead of killing them outright.  While handy, the deterministic nature of this rule is far too boring for my campaign.  To inject a little uncertainty into the proposition, I use this house rule.

• If you "pull your punches" and attack at disadvantage, and knock an enemy to zero hit points, they are knocked unconscious instead of killed outright.
• You can also attempt to knock out a target by making a normal attack roll followed by a DC15 DEX(Medicine) check.  If you are using a bludgeoning weapon you have Advantage on this check.  Success indicates non-lethal damage.