Honestly it is just getting to know all the skills and how to use them. Drop living meteor in a direction in which enemy heroes will be walking or parallel to structures (such as if you're pushing a lane, drop it vertically to the screen to hit the bottom tower, gate, then top tower). Use empower sulfuras to try and target heroes or large groups for maximum effect. Use your blast wave ability on yourself for some AoE damage (alt + E) or on yourself or other heroes to help them escape/engage (because of the speed boost). Use your Molten Core ability to defend structures or even go on the offensive in team fights.
For your ult, you'll want to pick up Lava Wave almost every time. Sure it is better on certain maps than others (it isn't that great on Blackheart's Bay), but it has an insane amount of push. Currently, builds that go with Lava Wave have a win percentage of 65% and Sulfuras Smash have around 54-55%. Even though Lava Wave can be easily dodged by many enemy heroes, the wave is worth it for pushing especially because it can be upgraded to two charges. Not only that, you can sometimes even surprise enemy heroes who are currently overloaded with focusing on a team fight and get some easy kills. At the very least, it can push a lane while giving your team the availability to retreat without getting chased.
All in all, great hero for pushing but not as much for picking off heroes in team fights. Once you learn to fill that role and get a feel for the skills, it is all about just practicing with him as much as possible.