One thing I learned the hard way quite a few years ago is that it's a good idea to keep backup copies of all your most important files. Probably seems like a no-brainer to a lot of people, but there was a time when it never occurred to me. And after I had a few computers eventually snuff it, I wised up enough to back up my writing and most important photos to a CD, then a few years later, to DVD. But the process was kind of a pain and I only did it sporadically, and as a result, when a critical component of my computer crapped out on me, I lost some vital files--the most important being the stories and novels I was writing and rewriting.
It wasn't until a couple of years ago that I discovered Dropbox. I had used Syncplicity for a while before, but had certain problems with it. I tried Dropbox and have no troubles at all. Copy the files you want to back up into the Dropbox folder, and it's automatically synced to your online account. For example, if you're working on a novel, every time you click the save button, the newest draft is uploaded. And you can access your files from any computer, which brings me to the other kind of backup for which I've found myself desperately in need.
It's a good idea to have a secondary computer, because you just never know when yours is going to fail to power up, or have a hard drive die, or have something inside it explode. My personal setup is a desktop computer which I built myself almost four years ago, and a laptop that I use as my backup.
One of the benefits of building your own computer, aside from being able to put together a kick-ass gaming system without spending $4,000 on one with the same specs, is that by learning what the parts are, what they do, and how to put them together, you can save yourself even more money in the long run. Before I decided to buy the parts and build one from scratch, I would simply go with store-bought computers, and of course, when one component died, I assumed the whole thing needed to be replaced. I don't even want to think about all the money I spent on new computers when I could've just replaced one part for a fraction of the cost.
For the computer I built in August of 2009, I spent about $800 for the parts, and have been using it ever since. The power supply unit I bought for it lasted three years before it gave out, and I just replaced it with a new one and kept going. But there's some down time while waiting for the new part to be shipped, and that's where the secondary computer and Dropbox come in. Before I was able to get hold of a good laptop, I wouldn't be able to keep working on my novel or whatever else I had going at the time.
Same thing when I needed to upgrade the processor and motherboard. Since neither had actually quit on me, I was still able to use the computer, it was just that the old mobo caused the video to hang up two to three times per second (sort of like a visual "stuttering" effect) while playing newer games such as my current favorite, Saints Row: The Third. So I ordered a new mobo, and because it wasn't compatible with the processor I already had, I needed one of those, too. Luckily, I found a sweet, 8-core one that came in a bundle with a motherboard. Installed it, and had a few hiccups. I'm good at putting the hardware together, but not that good with software, so I wasn't able to fix the problem. Took a couple days for the repair place to get it working, but fortunately I had my laptop at that point, so I was able to continue writing uninterrupted.
And again, just a few nights ago, the new power supply blew up. I'm not even exaggerating. Everything was fine, then suddenly, it sounded like someone fired a huge shotgun right beside me. Two or three horrendously loud bangs and my computer shut down and wouldn't start back up again. And I just about shat my pants, it startled me that much. It happened around midnight, and it was after three in the morning before I finally stopped shaking.
So, I fire up the laptop, and once it boots, the latest drafts of my current novel in progress and various other stories I'm working on, automatically downloaded. Faster and easier than using CDs or USB drives or memory cards. Even though I'm eager to get my baby working again, I'm still able to write, keep in touch with family and friends (through Facebook and Gmail), and apply for jobs. And once the desktop is fixed, all I have to do is boot her, and all of my writing will download. Then I just launch my word processor, Atlantis, and each story I'm working on loads in its own tab.
Again, this probably seems obvious to some people. But it took me a while to figure it out, back in the day. And it was a while longer before I was able to pick up a decent laptop. So if there's one piece of advice I could offer other writers, it's to add both Dropbox and a backup computer--whether it's a second desktop, a laptop, a netbook, or even a smartphone (the Dropbox app is available for both Android and iOS devices)--to your toolbox, if you haven't already done so. Both of those have saved me a lot of trouble, and I wish I'd had access to them many years ago, when my computer would stop booting and I'd end up losing all my work.
So, the tl;dr version--always, always have a backup.