Major factory has an additional limitation in that it can only be placed on an originally-owned territory, so there are very few eligible territories to place new ones. You will almost never see someone buy one due to that and the cost.
Minor factories have an additional limitation in that they cannot be placed on islands. So all those islands in the South Pacific are ineligible.
In practice, 80% of minor factories will be UK placements in Egypt, Persia, and Iraq; and Japanese placements in FIC, Kwangtung, Kiangsu and Manchuria. In late game US will place one in Norway or Korea if given the opportunity, and sometimes you’ll see ANZAC place one in Queensland.
Airbases tend to be placed more than harbors. Gibraltar is a popular spot for UK and Japan will often place minor factory, airbase, and harbor all in FIC. Harbors are rarely purchased otherwise, although sometimes there are opportunities to place them effectively in Norway or in the Pacific. At 15 IPC each they are somewhat on the expensive side so unless you can really maximize what they do for you, keep your airbase/harbor purchases to a minimum.
Also, all these installations can be captured by the enemy, so don’t place them unless you can hold the territory.