Since it took me hours to find this answer, I decided to put it up clear and simple: this is how you 'force' your stock HTC Hero to check for updates.
First off, this is for the original HTC Hero. So not the Sprint or CDMA version, but the GSM version (with the chin). Most sites tell you to use the "Check for updates" option. The original HTC Hero firmware does not have this option.
Instead, you need to install the first (of three) updates to get the updater. The original update mechanism checks every two weeks for an update. If you need it to check right away, you can move the clock 2 weeks forward or use enter this number: *#*#682#*#*. If it worked, the number will disappear from the dialer and almost instantly a popup will tell you that an update is available.
After this update, force the phone to check for future updates by doing:
- From the Home screen, press MENU, and then tap Settings.
- Scroll down the screen, and then tap About phone > System software updates.
- On the System software updates screen, tap Check now.