I back up every day, I also have 2 back up drives, which you should also have, if your data is imporant to you.
A Time Machine back up, and a clone (which is bootable)
I use a OWC Elite,and a IOmega.
Use Time Machine on OWC:
http://www.amazon.com/s/?ie=UTF8&keywords=iomega+portable+hard+drives&tag=googhy dr-20&index=electronics&hvadid=3927029335&hvpos=1t2&hvexid=&hvnetw=g&hvrand=2132 262008473015365&hvpone=&hvptwo=&hvqmt=b&hvdev=c&ref=pd_sl_2k8gsvyzks_b
These are but a few that are available for affordable prices, I have had very good performance from both, there is going to be many other opinions, and all are valid, I just sat stay away from WD as they have been problematic.
Do a web search you will find tons of drives, at different prices, and capacities, choose one or better still two and back uo to 3 different systems.
I use Time Machine and Carbon Copy Cloner:
Also check into SuperDuper:
Hope this helps