The safest way is to set up redundant drives (raid storage). I use NAS which is basically hard drive storage that isn't in a computer. It's network storage. So on my home wireless network I have one of these connected directly to my router and working as a hard drive for all my computers in one location. Here is a cheaper example: (I've never used this particular unit, it's just an example since really good ones can be thousands)
http://www.tigerdirect.com/applicati...3662&CatId=207
I use desktops and laptops all in my home network and save all my edits past and current that I'm working on on my network storage. That way I dont have to mess with external hard drives and messing with taking them with me any time I leave but still want to get some work done. You can set up your NAS to have redundant drives so that everything you save is backed up on another hard drive the exact same way. This is good especially since you can get 1TB drives these days for under $200 from tigerdirect and newegg type places.
In my router settings I 'port forward' so that I can access my home network outside of my home so this way I can edit my photos no matter where I am in the world and not have to worry about backing up info or messing with external hard drives. I just open up my laptop and get working. It's the best and easiest I've found so far but would love to hear if anyone has any other options that they do.