Important abilities

Passive: Unseen Predator Q-skill: Savagery Ultimate: Thrill of the Hunt

Information

The triple resets do only work for his Q, not W or E because you can only store his Q ability, the W and E are used immediatly. There are many ways to triple Q, I will only explain the easiest way I know yet with 2 empowered Qs.

Rengar gets 1 stack ferocity for using an ability on an enemy. At 5 stacks he resets his main abilities, causing him to be able to double-Q when using Q at 4 ferocity. His ultimate generates 5 stacks Ferocity over 3.75 seconds (1 Ferocity in 0.75 seconds). Rengar can only triple-Q when he has his ultimate.

How to triple-Q

1. Get 4 stacks of Ferocity
2. Activate your ultimate. Your ultimate generates Ferocity.
3. You will reach 5 Ferocity after 0.75 seconds. Press Q when you have 5 stacks (press it multiple times, it's not easy), not later. Ferocity resets to 0.
4. Your ultimate continues generating 4 stacks Ferocity (takes 3 seconds). When you reach 4 stacks, jump on an enemy within the next 3 seconds, this will apply your stored empowered Q.
5. Press Q again and auto attack with a normal Q, you will get 1 stack Ferocity so that you are at 5 again.
6. Use Q and auto attack with another empowered Q.

This is what you can do if you don't have enough time to wait for your ultimate to generate stacks:

1. Get 4 stacks of Ferocity
2. Activate your ultimate
3. When you reach 5 stacks press Q, not later. Ferocity will reset
4. Now the new part: After the Ferocity reset you wait until your ultimate generated 2 Ferocity. Jump on an enemy and auto attack him, then use a normal Q, W and E so that you get 5 stacks
5. When you reach 5 stacks Ferocity use another empowered Q.

There are very good explanations for triple-Qing in the Forum and on YouTube. Search "rengar triple q" on YouTube. Rengar is incredibly strong at the moment and the reason why people are so successful with him even in high ELO ("only rengar") is because of this combo, even in lane you can one-hit enemies at level 6, especially in mid. It also works against towers: 1. You can jump to towers with your ult 2. don't get in range of the tower before you have 4 stacks because it will stop generating those stacks.

I appreciate when people tell me to change things when it is hard to understand or when I did a mistake in the explanation. It's almost as hard as T-spinning in tetris.