If you’re going up against more than two tanks or on a map where you have to melt a single target objective (like BoE), go for his Grievous Throw build. You can pump out absolutely insane amount of single-target damage with that build, I’m talking 3 heroes worth of damage to immortals constantly.
If you’re up against dive heroes or a lot of healing, I’d go for his Twin Cleave build. That gives you a little more poke/burst damage that would otherwise be difficult, and allows you to harass their backline and peel for allies a bit better.
If they lack much dive or sustain, go for his basic attack build. Headhunter makes teamfighting safer once you’ve completed it, and once you get Eye of Zul’jin you can chase down most mages, tanks, and rangers easily.
Early game, wail into the tanks. They have a lot of hitpoints and are great for stacking your quest. Don’t bother going for their squishies yet unless they’re already easy targets. Your teammates may yell “don’t hit the tank,” but that’s honestly the best way to scale into the late game.
If you don’t have any good solo-laners on your team and the enemy team doesn’t have feeder heroes like Leoric or Murky, I’d highly recommend against picking Headhunter. You’ll be too busy laning to stack it effectively.
If you do take Headhunter, make sure your team knows you’ll be rotating for ganks.
Take Taz’dingo if you’re going for his Grievous Throw or basic attack builds. Absolutely make sure your Trait is active during Taz’dingo. Amani Rage will give you a little more burst at the start of Taz’dingo and a little sustain left over after it ends, so I’d recommend using it right before you ult.
Guillotine is preferable if you’re going for his Twin Cleave build, but not always ideal. Amani Rage is immensely important here, as reducing your own health to boost Guillotine’s damage is super strong.
I’d always recommend going for the upgrade to your ult at level 20. I find that the reliability of Forest Medicine just isn’t worth the far greater but more situational healing you can get from Amani Resilience and Buzzsaw.