Make sure there are always tools. Always. As soon as you don't have enough tools anymore, your population will die very rapidly. I speak from experience
![Lips Sealed :-X](https://cdn.geekhack.org/Smileys/solosmileys/lipsrsealed.gif)
If you have a school, two people for the biggest farms and cattles are enough. Check if there is still unharvested food on the fields in winter, if so you need more farmers. Make sure you have a variety of food.
If you have a town hall that is a nice way to see how much food your town produces and consumes each year, always stay in a slight plus so if somebody grows up or a baby gets born, you can still provide enough food.
To check if you should build another house, look how full your houses are. You tend to build too many imo.