Build fields always 2x2 or 3x3 to gain fertility bonus. (Highly recommended: 5x5=25 for each crop so you may be able save the space for setting down the drainage pump, greenhouse,well,sprinkle)
Don't waste high Level items on low Skill workers. Example to train the work skill of a worker first use "Copper Hoe" till 100 than "Silver Pitchfork" till 150 and than "Golden Hoe" till 200. More see Items.
Farm ranking places
Shipment 20 million (#7)
Harvest 15317 (#1)
Tourism 2211 (#1)
Staff 252 (#1)
Your workers will work on crops of active missions with priority. Only try to do one "Very Hard" mission at a time.
To win the special livestock contest, the 'looks' attribute is the most important. Use the Mushroom House territory for the best effect.
You could potentially "farm" money late game by entering the Chimpan Z contest repeatedly.(However, at this point of the game... money doesn't really matter to you, its the research points that matter as you will want to try and max out everything in the game.)
See Bugs and cheats (Pocket Harvest) for more info.