The core principle with divine smite is that it becomes incredibly powerful when combined with critical hits, since all those damage dice get doubled. When you're setting up your character, make sure to check the reactions tab where you can configure divine smite to automatically trigger on crits, which makes things much smoother during combat. A regular divine smite using a first-level slot deals 2d8 radiant damage, but when you crit that becomes 4d8, and it gets even better with higher-level slots.

Something interesting to keep in mind is that when you're fighting fiends or undead, you get an extra 1d8 damage that also doubles on crits. The real fun starts when you combine this with gear that helps you land more crits, like the knife of the undermountain king or sarevok's horned helmet. If you really want to maximize your damage potential, try using hold person since it guarantees critical hits on melee attacks against the affected target.

Tip: you might want to save your spell slots for when you actually score a crit, since that's when divine smite really shines. The game will show you the potential damage range before you commit to using the ability, so you can make an informed decision. And if you're playing as a half-orc, you'll get even more dice on those critical hits, which can lead to some absolutely devastating damage numbers especially in the later parts of the game.