Starting a Smiter
Create a Paladin from the Create a Character screen. Assign a name to him, and decide which realm type to play on (ladder, non-ladder or hardcore ladder). Level your character to 40 by completing all quests in each Act, doing runs in the Secret Cow Level and completing the Ancients quest. Join public Arcane and Tomb run games to expedite the leveling process.
Nightmare and Hell Modes
Defeat Baal in Act Five to progress to Nightmare mode. Reach Level 60 by doing the same thing you did in Normal then, defeat the Ancients and Baal once again to reach Hell mode. Reach Act Five of Hell mode and join public Baal run games until you are at least Level 75; the higher your level, the more effective your Smiter will be.
Stat Points
Equip any items you have that add Stat Points, then put Stat Points into Strength until you reach 138, which is the amount required to equip a Vortex shield. If you want the maximum Chance to Block, which is recommended for players on hardcore mode, open the Character screen by pressing the C key. Add points into Dexterity until your Chance to Block reaches 75 percent. Put all remaining Stat Points into Vitality, which gives you more health; don't put any into Energy.
Skill Points
Max the Fanaticism, Smite, Holy Shield and Defiance skills by putting 20 points into each one; these are the main skills used by Smiters. Spend any remaining Skill Points on anything you want.