Best Price Computers asked me to do a sponsored post on their
glossary on data recovery. Their glossary offers some basic information about what you need to know about data recovery and a bunch of links to other pages with more information about specific things link RAID (Redundant Arrays of Independent Disks), backing up data, disaster recovery, ...
So in their article Best Price Computers first gives some basic information on data recovery, then they give some examples of data recovery and also some info on what you can do wrong like opening a HDD yourself to see if you can fix it. That's not a good idea because there's not really something in a hard drive you can fix yourself. Opening it will do more harm than good as small pieces of dust can do your disc a lot of harm.
The article states that prevention is better than finding a cure. Which is true of course, it's better to have a backup of important data than having to hire a specialist to recover the files from your hard drive. Having backups will often be a lot cheaper and quicker.
Overall it's a pretty good article if you really know nothing about data recovery, you can read it over here.