Look for ATA protocol´s and read about ATA registers, im going to put my idea about learning about data recovery on this post , because im think its need it .
On my case one good people some years ago from Brazil , begins to teach me about hard disks, data recovery, etc wich was this method wich he told me?
Read Books, read documents like , many times i ask him for quickly solutions like" can u teach me how to do a head exchange, how to repair a SA; etc" and he told me, "Data recovery its not a push button solution, u need to study, learn, think on Hard disk, etc," my first imprresiion was " he is a bad people because , he doesnt want share with me his knowledgement about Data Recovery, SA, structure, electronic, mecanic,head exchange, diangostics, etc on one word Engineering on HDD´s but he told me the only way , in wich u can learn about hard disk engineering and data recovery, its by u self. with your own cases,with practice, looking the hdd how works practice with dummy disks, etc reading, books, understanding the mechanism of hdd´s this was some late for begin to understand this but thanks GOD now, i can said " Thanks friend because on this way u force to me to understand the best way to learn abut HDD engineering many thanks and sucess ." So this is my suggestion because im start from this way, its hard, need nights without not sleep, need many patience, practice,think on Hard Disk, think on whats happening with this cases , and the most need to understand its not a easy work like many people think , im buy products " tools" , but this tools they are not solutions like " next--> next--> " Finish

Smile Data recovery! from any cases!
My suggest
Begin to understand on fist low level work´s what does mean low level "problems until hard disk are detect by BIOS read about Logical Structure MBR, PT, VBS, NTFS, MFT, FAT etc , im suggest this book "Upgrading & Repairing Pc´s " From Scott Mueller, here are some useul links
U can use programs like winhex to understand, sector level´s , after u get all of this begin to read and understand the protocol command between HDD and Host, ATA protocols, registers, commands , programs like mhdd,victoria, hDDL are very good for understand some of this. this is only a little.
ATA protocol´s
http://www.t13.org/Documents/Default.aspx?keyword=ATA.
http://www.ntfs.com/ntfs-mft.htmBest Regards
Sinceraly
Alberto Pavón