Tips on my team to beat the elite four (Heart Gold)?

Buy a lot of revives and hyper potions. With Ho-oh, get rid of extrasensory. It's basically useless. I also recommend catching the roaming legendary pokemon Raikou and Entei. It may seem difficult to capture them, but it is much easier than it seems. I had to do it also and my team was spectacular. Always keep your strongest pokemon alive and at full health. It doesn't matter if they die, just be sure to bring them back to life and heal them. Keep a lot of full restores handy, as they are quite useful. Teach your pokemon moves that are relevant to their elements and with high PP, accuracy, or damage. Always heal before a battle and don't be afraid to lose. You will have to if you need to start over. It sucks, but sometimes it is neccesary. If you try to heed to these guidelines, the only real problems you will have are with Koga's Muk, and the champion's pokemon. And when the elites use full restores on their pokemon. It is very annoying. Best of luck to ya!