The Farmer’s Almanac contains a list of the current quests you can undertake. Generally, quests require you to have, make, or sell certain goods. The reward for quests is usually experience and sometimes keys.
If you start a quest after you’ve already created and sold a particular good, you’ll have to do it again to get credit for the quest. Try to focus on completing the quests in order, rather than just creating and selling new stuff as fast as possible. That way, you’ll get the maximum possible rewards with the least amount of effort.
Whatever you do, don’t neglect the Farmer’s Almanac, as it’s one of the primary sources of free keys in Farmville 2: Country Escape.