Power Supply Reliability
Lately, there are a lot of power supplies out there that just don't get the job done. A very rough by easy method of figuring out power supply reliability/strength is, believe it or not, its weight.
The more a power supply weighs, generally, the more powerful and reliable it is. When you think about it, it makes sense - the more a power supply weighs, the more "stuff" there is inside.
Don't overlook your PSU - it's very often neglected, but it's a very crucial component - having a reliable power supply unit is paramount for a good build.