First, start off with a Dorans blade for the extra attack and HP, along with the skill Ruthless predator, for the stun chance.

I recommend buying the Ionans boots of lucidity for cooldown reduction, which Renekton earns alot on, thats why you buy a Yoomuus ghostblade right after it.

When you level add points into Cull the meek, for minion farming, and then slice and dice for increased mobility and minion farm. And then add into Dominus as soon as you get a chance. Add into cull the meek or ruthless predator depending on if you want to focus on attacking champions, or minions. Cull the meek for minions and ruthless predator for champions. Dump the remaining points into slice and dice.

A frozen mallet is always good for melee champions, so go with that too, for more HP and slow effect. Buying a bloodthirster for damage and lifesteal is great too. Finish off with a Trinity force which you build by buying sheen. When you got your full build you can replace the dorans blade with either another bloodthirster or a phantom dancer (Wormog armor works aswell).

When you are going to attack an enemy champion, first use slice, then stun it with ruthless predator, and as soon as they start to run, use dice to get closer, and use cull the meek, then ignite if you have it. If this wont kill the champion repeat the skills as soon as cooldown is off. Flash to them if you want to ambush or if they are running away. Use Dominus as a "heal" as it gives you 300 hp.