Battery tips

Am awaiting delivery of an Alienware 18.

I've seen conflicting battery advice to prolong the life of the battery long term, ie it's ability to hold a charge.

Is it better to leave plugged in at all times unless I need to run on battery (which I know is limited on a robust system like Alienware, I'm expecting 2-4 hours tops depending on what I'm doing, and likely less than 2 for graphics intense tasks)

-or-

Is it better to unplug and let battery run lowish and then plug in

-or- 

Should I leave plugged in but periodically - like monthly - allow battery to run down fully?

Would appreciate both the official "manufacturer" guidance/battery maintenance instructions and real world advice from those with experience.  

Thanks