If you get kuma remember to protect yourself, you die, kuma dies
Remember when kumas out you can still fight, don't know how many people I've seen that don't do anything
use different combos for different situations don't rely on just one.
Try to make your combo have some form of Ariel it makes you less likely a subject of a random super thrown out
Don't jump into a fight without thinking. Hei is fantastic at cqc but more then one he's goin to start to struggle
Remember kuma is a chance you may not get a kill at all so it may be worth to save for level 3 insta kills
Don't rely on forward square as a kill confirm as most hei's do
Always use an attack when you flutter to the ground, something unique and hugely useful for hei
Using O forward then triangle forward x2 in the air can make you gain alot of distance in the air which is really useful to escape others supers.e.i raidens lv2 after the freezing part when they come after you to try and kill you twice or escape another kuma
Use red fists, extremely useful, try n do it when kuma is out
Hei's O forward can dodge some projectiles which can make getting to spammers really quick then running and jumping etc
Hope this helps. I love hei, he's a really fun character to play with
Don't be afraid to use your up throw to start combos. Up throw, forward triangle, down triangle works pretty well. Your air down triangle shuts down a crowd pretty well. And if you miss it, use the triangle wake-up attack, or the forward circle wake-up if you're too far. Your up circle should irritate opponents just enough to get them near you, too. Your goal as Heihachi is going to be to single out your opponents. If too many start appearing around you, you might want to knock them away with Triangle or Circle-Square.
Edit: I was curious about combos and the like, and stumbled across a pretty informative video. Has some pretty nice Heihachi combos in it, actually.
Fresh to death