[Updated with in-store pickup news] In the US, online preorders for the
iPhone 6 and 6 Plus will begin at 12:01AM Pacific time Friday morning. While Apple has yet to announce an exact hour, AT&T, Sprint, and Verizon all have, and traditionally Apple has opened up preorders at the same time. Other vendors, like T-Mobile, are referencing a broad September 12 window.
Some retailers participating in Friday preorders -- possibly later than 12:01 -- include Best Buy, RadioShack, Sam's Club, Walmart, and Target. The phones will only ship on or around September 19.
Update: Checks show Apple will allow in-store pickup for preordered phones.