Hi M,
I second the advice to checkout the other mentioned threads.
Here is a quick guide:
Whatever airline you are using to fly to USA, use a US domestic airline that has an interline agreement with your transpacific airline. So you luggage can be checked through to the final destination.
Eg Qantas will interline your bags through on most domestic airline, VA will interline bags with fewer airlines, UA same.
In the main most domestic airlines in USA are the same once you peel off the exterior facade.
Re phone:
Go to the US to your final destination. Then go to an ATT shop and get a prepaid sim card for 65/month - will give you unlimited calls in USA, and 2gb data, and unlimited sms to australia and about 100 minutes calls to landlines in australia. You will need unlocked phone. You can get sim cards sent to you in Australia but the costs rise for the postage. In transit use your australian sim card on global roaming and look at your global roaming charges before you leave - you may want to get the phone company to turn off internet on the day you leave. Just turning off internet at the phone is NO guarantee.
this is just a quick summary. have a look first at the other posts first.