Last time I played Heart Gold, I did a little bit of training. I rematched a couple of Gym Leaders and then took on the Elite Four again. I decided to use my Clefable against Lance, because I don't really use it that much when I battle the Elite Four. Clefable took a long time to set up (having to use Calm Mind 6 times + having to keep Reflect going), but once it was done it managed to sweep Lance's whole team. It grew a couple of levels as well.
I then tried headbutting trees for the first time on Heart Gold. I tried looking for a Pineco so that I could get a Forretress and trade it for Steven's Beldum, but I didn't find any. I did, however, manage to catch a Heracross.