Another tip for people. This one is a little bit wordy, so bear with me.
Don't know what to upgrade with your builder? Can't decide where the best place to put a farm or a quarry is? Well...
So, the first part of this tip is if you hover over an improvement in the build menu, e.g. a farm, it comes up showing the yields on each tile. Obviously, the one you want to upgrade is the one with the greatest value. So you want to look for, say, a tile for a mine with an improvement of 7, 7.5, 8, etc. rather than 5, which is the base value. This is what the improvement will produce once it is built (I believe).
But Loerwyn, I want to know where the best place for an improvement I don't have yet is! Fear not, your majesty! One aspect of the build menu is it has 5 tabs, labelled G, W, R, U and C. 'G' is the default setting, showing the most relevant actions you can take. W is for Wonders, R for Rural, U for Urban, C for Culture. Selecting 'R' will show you ALL possible Rural improvements and tell you their requirements, and like ones you have unlocked, if you hover over the option it will show you the possible yields over each tile.