Couple questions regarding my first time with Avis.

1) What is Preferred Service? Do I need to qualify for it? If so, how do I do so? Will my corporate program affect this in anyway?

2) Is the USAA rate the lowest out there?

3) Can I double dip points? If not, are the Avis points more useful than sending them over to UA?

4) Anything else I should know/do?

Thanks!