Migrants

Getting new migrants
Watch your colonists' expectations. If any expectations are yellow or red on any colonist you will not get any migrants. Every colonist must have green 'satisfaction' in all Expectations before the timer will start for migrant arrival.

Your bonfire serves as a beacon for migrants when they arrive. Selecting the Bonfire object will show a tooltip indicating whether or not your current colonists' expectations are satisfied and, if so, how long you can expect to wait for a new migrant colonist to arrive.

Children:
Children are an alternative to migrants. Migrants are a lucky dip. What arrives is what you get. With Children, you can nurture them. You can dictate how many good (and bad) traits they get and how much skill they start with. Children can't work. So if you use children to expand your population, make sure you take the time to nurture them, else you may as well have just grabbed a random migrant.