Essences is always a priority for me, even if the total yeld is inferior to a nearby cell. They add flexibility, and many city enchantments scale with your #of essences.
Then come the purpose of the city.
City: i want high food, unless I'm later in the game and I have a lot of Grocers around the kingdom
Fortress: again high food, even over production. They are the city I want to grow faster for the unrest bonuses they get at level 3 and 5, and they also get growth malus. They also lack a "Produce X" strenght contrary to towns and conclaves, so I don't have hurry to build all the facilities, making high production less desiderable.
Main fortress: the highest essences yeld I can find, for troup training city enchantments. By main fortress I mean the one that will stack all the training facilities.
Conclave: high production, they have a lot of long time facilities to make, and the faster they get them, the more time they spend producing research. High city level bonus are not that great, so food is somehow not an issue.
I almost always avoid 1 grain tiles, they are a pain. 2 grain is bad but acceptable for secondary importance cities.
Also when you chose mind avaiability of nearby rivers (a bit of +food, +gold), forests/clay pits (+production).
