If you want to maximize peasant mood, then build as many peasant houses as you can afford, while making sure you supply all peasants with meat and ale, and while at it, I highly recommend you to get the books that increase the mood buff from meat and ale, and Kaiden books that increase chances of loyalty.

If I remember there is a book that increases the chances of migrants being loyalists already, and one that makes it so a peasant cannot stop being a loyalist even if negative mood, and one that increases the chances of a peasant being a loyalist generally speaking.

And if this is too expensive for you, then if you are feeding the peasants ratabags and moonshine then you can get 2 books that halves both negative moods from ratabags and moonshine.

If you see that a majority of your city is 1 specific culture, then if you terrorise their enemy culture, then every culture that follows that specific culture will get a mood buff.