Use write protection. To prevent further accidental destruction of data, mobile storage devices should be mounted as read-only whenever possible before you attempt any recovery operations. SD cards typically have a write-protect switch, which makes it easier to protect them before attempting a recovery operation. Removable USB drives are a stickier wicket, since Windows does not have a way to manually mount their file systems as read-only. There is a Registry setting that works with Windows XP SP2 and higher; it forces all USB mass-storage devices into read-only mode. (Note that any program that expects the device being recovered to be writable, such as Remo Recover, may balk at this.)
Be patient. If you're using a program that supports deep scanning at the cost of a slower recovery process, use it. The speed of this type of scan depends on your system's CPU rather than its I/O, as most of the work involves matching file signatures and checking for false positives. If you're in a hurry, run a deep scan using the fastest machine you have access to.
Remember to use the "Safely Unplug Hardware" option. Memory cards and sticks generally tolerate immediate removal, but do yourself a favor and remember to safely eject these devices before removing them, just to be sure. This cuts down on the possibility that data will be lost in the first place.
OS: DOS, Windows 98 and later, Mac OS X, Linux (2.4 /2.6 kernel)
In some ways, PhotoRec is the most powerful application in this review. It can recover files from almost any device -- whether or not it's mounted with a drive letter, has a partition or is even formatted. PhotoRec has editions for multiple platforms: Windows, Linux and Mac OS X. And its creator claims it can detect and recover more than 390 types of files, and not just photos, as the name might imply. However, its very Spartan interface may be off-putting to users who expect a slick graphic interface.
When you launch PhotoRec, you're given a list of all the available storage devices in the system: hard drives, attached removable drives or loaded card bays -- but not networked drives. Choose a device and a partition, set your search options (the defaults work fine for basic recovery), pick a place to save the recovered files to and the rest is pretty automatic.