I have an ASUS motherboard and recently went through the process of updating the BIOS. One of the things worth nothing is that it is not safe to just get the latest version and try to run EZ-flash. Some of the updates will update EZ-flash as well and those become required for installing later updates.

The download page actually has release notes which specify when a certain BIOS is required, but you basically have to read back through all of them to figure out which ones to install.