So make sure you produce everything you need for efficient development, and don't worry, you won't be in danger of overproduction.
Put one (two*) action cube on a warehouse area on your player mat. Manufacture up to as many products as the number of buildings of this type constructed. Place product cubes in the respective warehouse and pay the specified cost for each item produced.
In your turn, while choosing the production as your main action, you can manufacture several times, the same or different products, spending action cubes each time.
[*] If there are any action cubes on the warehouse already, thus you have already produced there in the current round, place two action cubes to manufactured on that wearhouse again.
Mike chooses production as his main action. He has 2 meaderies, one artisan yard and three forges constructed. He decides to produce weapons and fabric.
He puts an action cube on the forge area on his player mat, pays 3 
+ 3 
and manufactures 3 
.
Then he puts an action cube on artisan yard area, pays 1 
+ 1 and manufactures 1 
.
Mike lacks 2 for his army training plans, so during this turn he activates his forges again. So he puts two action cubes on forge area, pays 2 + 2 and manufactures 2 more. Then he passes the move to the next player.
Note that he did not produce in the meaderies, although he could. Perhaps, he is not sure how much of mead he would need yet, or he realizes he lacks food for his army training plans. In any case, Mike can choose production action this round again to produce in his meaderies, forges and artisan yard.