Now the most important thing a heavy can posses, accuracy, accuracy will keep you on top of your enemy and turn him in to something similar to ground beef/cat food in a can. If you're able to trace your enemies well you will go far as a heavy. Practice tracing by loading up quake with the -game teamfortress or where ever you unzipped your tf pak files to. Then go into the game and start up the regular levels of quake, use the GOD command to become, well... GOD. Use the monsters for target practice, or rather tracer practice I should say. This will help you out more then you know in long run, and it will help you get used to the feel of the cannon, and it provides a good practicing platform for later manoeuvres.
It may not seem like it takes any brains to stand in one spot and fire, but as mindless as it seems there are still tactics that you need to know to stay alive. The most important of which is to find a spot that is good to fire from but does not leave you exposed from another point, and which does not let your enemies circle strife you to death. Also NEVER EVER forget that you have grenades, to do this is to cost you frags that you other wise would have missed. To forget your grenades also leaves you no way of defending your self when your auto cannon is useless (out of shells/cells). So remember bind 2 keys to +gren1 and +gren2.
Example:
bind x "+gren2"
bind c "+gren1"
Use your head, THINK, don't just react, reacting will only get you so far, but thinking, thinking will get you even farther. I like to refer to the hwguy as the thinking mans class, namely because he is slow, cumbersome and runs a high risk of being killed because of his stationary nature. Think of it this way:
You are confronted by 2 players, a soldier and a sniper, you happen to be on there balcony because you took a wrong turn on the way to your flag room (in other words you didn't take my advice and stay in YOUR BASE!). The sniper see's you as he rounds the corner coming from his upper resupply and the soldier is coming from behind you. Who do you kill first? If you said the sniper your already on your way to becoming a very good heavy. Plain and simple, you see you can probably stand 2/3 rocket blast before you die, but one sniper bullet to the head and your toast. So take out the weaker target with the stronger gun (the sniper wizard) then kill the soldier (or get blown to hell, which ever comes first). Also do not kill the sniper, then unwind your cannon, turn around then wind back up again. If you do this you will die for sure, no if's, an's, or but's about it. Don't believe me? Ok lets do the math 1.5 sec's to wind down the cannon, and 1.5 sec to wind up the cannon, plus the .5 sec to turn, that adds up to 3.5 sec's. Now in that 3.5 sec's the soldier can pump out 3 rockets which WILL kill you, but if by some freak of nature your not dead you will be damn near it. But if you just whip around and keep the barrel's blazing that 3.5 sec is cut down to .5 sec and you have at least a fighting chance against the soldier.
Now for those of you that just lust for action an carnage, and go on offence with a heavy I can only offer you this advice. Avoid targets that are very dangerous (ie. soldiers/demos/medics/ pyros) and go after week classes (ie. engineers/snipers/scouts) they provide the quickest easiest frags possible for a hwguy. But it will happen if you stay over there long enough, hell it will probably happen even before you get to there base; you will meet up with the 'harder' classes. The ones that DON'T go down easily, and its things like this that fuel you to stay in your base rather then go out side, in what is for the most part a wide open area until you reach there base. And wide open area's and hwguy's do not mix I don't care how good you are at tracing. Oh you may think your fine and that tracing out side is no big deal, hell you may even be rocking ass out there doing it, but think about this:
If your outside in 2forts, between the 2 bases, your in sniper country and snipers are not very forgiving when it comes to slow targets (ie. YOU!). To a sniper, at long range that is, you are considered just an easy a frag, as that sniper is to you when your up close and personal. One well placed head shot will kill you, no questions asked, and if you hit in the chest you will survive for about as long as it takes that sniper to aim and fire again. Or for one of the other classes to blow your weakened slow ass away (one rocket when you have 50 armor, an 50 health WILL kill you).
Don't be afraid to turn tail and run for cover if you're under attack and near dead, most of the time if you do this you can toss a mirv in front of you and keep on truck'n. That other guy what ever class he may be will walk in to it while trying to kill you, or he will stop and wait for it to blow giving you that head start you need to make it to safer, higher ground. Where you can recharge your ammo, health, and armor. And if you team is any good you should be well protected from attack because that guy will be more interested in the guy that shooting at him then that big hwguy running away.
Ramp-room D and you.
The heavy can do very well on ramp-room D if he knows where to stand, now there are 2 places you can stand that will give you optimum frag rates and hi efficiency.
#1. Right at the top of the short ramp, this place is good for frags but you will often get your ass rocked by more skilled player's, now mainly demomen will give you the most trouble if you use this spot. But, from my experiences any class that knows where people stand, and play's at least half way smart will be a threat.
#2. The narrow walk way leading to the drop down point. (the big room with the large tunnel and lift, DUH!) This spot is my favorite if I'm on ramp-room D because its (at least from my point of view) easier to get the jump on incoming enemies, but it does have its hazards. Soldier's become a real problem, its very easy to get knocked off this high perch by a well placed rocket, and pyros with there fire rockets also fall in to the 'most dangerous' of the incoming enemies list.