That was my preference in G&K(as GEM isn't ready yet) :
- Great Artist,I usually favor Landmarks over Golden age,before Renaissance era or before National treasury and Hermitage are built;
- Great Scientist,I favor Academy over bulbing,before Atomic era .
- Great Merchant,I always use it for trade missions,because of the sum of both short-run(plenty of

) and long-run(+30

) advantages it provides;
- Great Engineer,always hurry wonder and when there's no Wonder to rush,I create Manufactory with it,except if I'm playing with Sweden(in this case,it's more profitable to give it to a City-state);
- Great General,I use Citadel to grab resources/Natural wonders from city-states . I even developed an exploit strategy for that;
- If I'm spawning Great Prophet(because I found a religion),the order is always: Found religion>Enhance religion>Holy site>Holy site . But if for some reason,I prefer to not found a religion,then I'll always built Holy site,specially if there's a civilization nearby who will found Christianism or Islam(as Cathedrals and Mosques will consume the faith generated by my holy site);