The trick for me for the smaller, less visually identifiable countries was to create linked countries - if I get one, I get its partner(s).
For instance, in Oceania (is that the name for the stretch between SE Asia and the US?), all countries are linked, based on perceived connections in naming.
Indonesia-Micronesia (usually the easiest because Indonesia is huge and I get visually reminded to enter it)
Solomon Islands-Marshall Islands
Tuvalu-Vanuatu-Nauru
Fiji-Kiribati
Samoa-Tonga (a stretch, but now it's etched in my brain)
Palau-Papua New Guinea
When I started, I always entered Swaziland right after Switzerland. Once I figured out where Swaziland was, I no longer had to link it, because it's large enough to be visible. Now I enter the names in order from North to South, West to East, starting with Canada - except I always start with Antigua, Sao Tome, and East Timor, because they are the ones that trip me up the most.