I use Image Recall - friendly "Don't Panic" on the front of the box
Three-layer strategy.
1) on the day, transfer images to Phototainer
--- confirm they got there by checkin 1st and last image numbers on each backup
2) at home, transfer to the PC
---- confirm that the files are all copied
3) convert RAW files to JPEG
--- make adjustments as necessary
4) resize JPEG to 640x480
5) transfer all from PC to DVD
6) copy from PC to external USB portable HD
7) when the 200G drive fills up, erase files from PC
8) when the external USB 200G drive fills up, buy a new one
So I have many copies.
Phototainer (emergency backup) - of only 40G
DVD backup (used to use CD)
External HD archive (one disk per year)
Internal HD working copy
I think that's enough
Though I may turn to making extra backup DVDs of the RAW files.
Tips?
1) Keep up to date.
Your images are only as good as your software and hardware !
Camera firmware
CD/DVD drive firmware
Computer operating system
CD/DVD burning software
2) QUALITY
Don't buy cheap media and expect your images to last forever.
On the other hand, I lost 3 Memorex CDs burned on the same day as a Kodak CD
I've had 3 of 10 DVD-9 from Verbatim fail to burn (no idea if the data will last)
Big brand names on the media may not help
3) Watch out for static
Dry, dusty conditions especially - memory cards are vulnerable
4) Watch the little light
Your camera probably has a light to tell you when the card is in use.
Don't switch it off, or remove the card, while the light is on.
5) Eject the media
Your PC or Mac should have a way to eject the memory card
Use it to make sure all data is flushed before removing it
6) Don't delete.
Buy more memory cards if necessary.
You will, one day, delete that really good image instead of the duff one next to it.
7) Don't keep duff media
You could use it by mistake !
My !G and 340M Microdrives are now very small doorstops.
My 512K card is almost history, it doesn't work in the 20D.
My RAW pics are backed up on my local machine to another drive, on a separate external harddrive and then to 2 different cloud accounts (nightly). So I should be good.
First of all we all can save ourselves from this nightmare if we keep a backup in at least 3-4 places.
Free Cloud Services( drive, dropbox etc)
Paid Cloud Services
External Hard drives
Other External medias (SD cards, USB drive etc)
Also there are certain third party recovery software. These Software use the technology to scan your device for lost photos, preview them and recovers them at your desired and specified location.
reference: Photo Recovery Software | recover deleted images & videos