What to backup?This is the first question I would ask myself. What do I want to backup? Actually we can divide this subject into several points.
Should I delete photos and keep only the best? This is a hard part when going through the photos of a session. For some photos the answer is obvious, either because the photo is brilliant or because it is totally worthless. For others chosing can be a pain. It is up to you. As far as I'm concerned, I do not like to delete photos, I'd rather create a separate folder for the best shots and leave the rest at the root.
Another side of the what to backup question is about the format of your files. If your camera only renders JPEG files, you can skip this question, just leave it as it is. The question remains if your camera can output RAW files. These files are ideal for image editing. They contain much more data that a flat JPEG file, thus are heavier, but they let you change many parameters like the white balance. Although you might not be into image editing, it would be a shame not to generate and keep RAW files. You should know every manufacturer has its own RAW format. The DNG (Digital Negative) file format is an Adobe open format which is meant to be a standard for RAW files, often much lighter than other RAW formats. Various applications can turn your RAW files into DNG files. It can be a good solution for the weight, the problem is that it might not be compatible with the editing software that came with your camera (if any). It is still compatible with many editing softwares.
If you want to keep your RAW/DNG files (which I recommend), you still might want to keep a JPEG file for browsing, showing to your family and friends, etc. Here is another advantage of DNG format: it can embed a JPEG preview file.
Hard drive or disk?Storage costs have been dropping since the first computer came out. There is no doubt it will keep decreasing and that's good news for photographers who are avid consummers of storage supports.
So now comes the question of where you want to backup your files.
We used to think disks (CD/DVD/BD) were the way to go for storage. It is read-only or at least you won't erase your data by mistake as the process of erasing a disk has its own menu on your computer. This is also one of the flaws of disks, they are not fast and easy to write to, update, modify. If you want to rename a single file, it is complicated. Another problem with DVDs is that they are fragile: scratches, fingerprints, etc.
The other option you have is hard drives. Very easy to use and maintain, they now fit many gigabytes in your pocket. Their price has become cheap. But just as disks, they are quite fragile, you'd better not drop it while it's on, even from a few centimeters.
When you have compiled years and years of personnal or professionnal photographs, they are extremely important to you. It would be terrible to lose them. A hard drive could be stolen, a DVD could be scratched, or even worse, your house could burn down or be flooded. What seems like a good solution would be to duplicate your backups, give some to reliable friends who live elsewhere and keep the rest. Great, but so very much complicated to keep up-to-date!
The truth is out there. I believe the answer lies on the internet.
There are websites (companies) that offer to store files for you. I hear you, they will undoubtely keep your data on hard drives, right? Right. Hard drives. Mirrored. Duplicated. And if the company is good, data will be placed in different datacenters in various places around the world. It would take a major catastrophee to erase your data!
Many woldwide companies propose such plans, Amazon, Google, some sites even propose unlimited storage plans like livedrive, carbonie. I have not tried these solutions, but I sure want to!