iPhone 6 and iPhone 6 Plus pre-orders have just gone live in most parts of the world on most carriers. That means if you hurry on over to store.apple.com — or a local carrier if you really want to — you can order just exactly the screen size, metal finish, and storage capacity you want. (And if you're still not sure yet, make sure you read out iPhone buyers guide first!).
If the websites go down, remember to try the apps. The Apple Store app is always a good option. New flagship iPhones typically do sell out for first day delivery, with shipping expectations growing and growing as time goes on.
So, if you want a new iPhone 6 or iPhone 6 Plus, and you want to pre-order, do it fast! Then come back here and tell me exactly which one you got!
UPDATE 1: 12:01am: Apple isn't live yet. Verizon and AT&T and both live for some people, still hold pages for others.
UPDATE 2: 12:15am: AT&T and Verizon both appear to be live for some people, not others. Apple still not live.
UPDATE 3: 12:23am: Apple Store app is working for some people in some countries for some carriers.
UPDATE 4: 1:03am: UK Apple Store up and processing orders.
UPDATE 5: 1:08am: In-store pickup link worked for me at Apple Canada.