Especially the how-to subforum: http://www.romraider.com/forum/viewforum.php?f=33
There are a couple good things on the wiki too: http://www.romraider.com/RomRaider/Articles
It couldn't hurt to get some book, too. There are a few listed on the wiki.
And lurk in the Tuning Discussion subforum, read logs, ask questions about what other people see in logs, learn to predict what other people are going to say about logs, etc.
And get EcuFlash and open some different ROMs and read the table descriptions. If you have questions, ask them.