The game offers you to choose whatever villager you want at the beginning of the game. However, you might be stuck if you don't choose wisely.

Gender:
If you chose only males or females you won't be able to have children before a long time, or never, and the game will end when all your 5 villagers are dead.

What I usually chose:
3 Adults - 2 females and 1 male
2 Children - 1 male 1 female

Age :
For adults, pick those who are between 15 and 25 years old so that they live long enough. For children, choose very young children between 2 and 5, so that they can be used to collect mushroom for a long time

Skills:
Skills are not very important at the beginning, your villagers will learn on the job eventually.

Likes/Dislikes:
Pay careful attention to the likes/dislike of your villagers, for they can turn out to be problems. Some doesn't affect the game (like turnips, bushes, crowds) while some can be real disadvantages (dislike running).

Assigned task:
Once your game begins, chose one farmer, and use the two others villagers to be both searchers and builders. This is the fastest way to improve your village.

If you have more than one farmer before unlocking other food sources, the coconut tree risk to stop providing fruits for a long time and your village will face starvation.

Keep in mind that a woman does not work when she has a baby. If your only farmer is a female and has a baby, she won't provide food for the village. Same goes for doctors, a female doctor won't heal someone if she has a baby. If you're careful, you shall be fine! (sorry for the poor english !)