Pre installing speaker wire question

[abynum1]

Hey guys, I'm about to get some speaker wire pre ran behind some floated sheet rock.
I will be going with either the Polk RM6750 or the RM6880. My receiver will most likely be the Onyko 605/606 or maybe the 705.

The longest run between the receiver and the back two speakers will be about 15ft at the most.

So, I have a few questions:
1) what gauge and brand should I go with? I don't need,and probably can't afford, audiophile quality but I do want dependable.

2) Do you run a cable from the receiver to the 1st speaker, and another cable from the receiver to the 2nd ,or do you run a cable to the 1st and then a cable from the 1st to the 2nd?

3) Should I run 2 seperate sets of cables in case something happens to the
1st (although I cant imagine what would) I would have have the 2nd already installed for backup?
Thanks for any help!