To tag onto #12, the GIR is THE source, but you need to really read it, especially the commentary and definitions. Also, be aware that a lot of loan situations don't fit into a nice neat box when it comes to coding the HMDA LAR, so document your files on why you coded the squirrelly loans the way you did. Come up with written how-to procedures so everyone will code things consistently (ie what income to use, where to find it, etc).
And visit this forum often!
Good luck!