From: The Republic of Texas
A few things I'd like to add if I may...
For WC and island (Johnston, Palmyra, etc.), I build up ports to 3 or 4 before working on AFs as you can unload troops and supplies faster. Any big construction project in the RL needs it loading dock, roads and storage areas set up first before anything else is done.
For PI, DEI, Malaya, etc., I'll defend with what I have but not send any additional units to support, and evacuate everything that I can. For example, the POW and Repulse, just get them out ASAP, as they are doomed one way or another if they stay (possibly doomed no matter what). Pull out your planes, pilots, ships, etc. Once you get some experience you can try a different strategy.
As soon as you possibly can, in the first few turns, send a large, escorted tanker TF loaded with fuel to Sydney.
Set up hub-and-spoke supply networks like described in this thread. Troops and supplies will be delayed a bit due to additional loading and unloading times (another reason to build up ports first), but its much more efficient overall and easier to manage. Another RL example is UPS and FedEx and most major airlines all use the hub-and-spoke method. You can use point-to-point for dedicated runs as others have explained (resources from Hilo to PH), but try to stick with hub-and-spoke.
Getting your logistics networks established is probably more important than trying to hold on to everything, but you must be prepared to defend and keep any base you designate as a hub (Suva, Noumea, etc.). Make that the mainstay of your Pacific Ocean strategy.