Jason has an old HTC EVO 3D phone and would like to mod it with Cyanogen Mod CM. Leo says that's a good idea as HTC doens't update it's phones very often and it'll breathe new life into it.
Go to the XDA-Developers.com forums. He can search for his device and find not only the right Mod, but also tips and tricks on how to root the phone and install it. He can also find 'how to' videos on YouTube. He should make sure he's followed the instructions precisely. Leo also likes to use Clockwork to give him choices of different ROMs and recover when he needs to. It's also a good idea to backup the existing ROM and Clockwork can do that as well.