When do I use which doctrine?

Basically I want to know when I have to use which doctrine for land, naval and air. Right now, I am basically not using the naval doctrine as I don't use shops much (nearly not at all), still gotta understand how u use them ig. For infantry, I use either specialization if I have a specific terrain, stalwart if I see dangerous countries close to me or massed attack cause I find it funny having many troops, it feels kinda fun yk. For air I either go for the bomber boost line or the fighter boost line (don't remember the names) depending on what the air force of the others looks like. Am I doing it right or is something wrong? Thank you!