The way you plant your crops depends on your watering can abilities.
For a level 0 or a bronze can, you should plan them in the "Fat c"-formation, giving you only 8 crops, but with watering access to every one. With a silver can you can reach over to a second crop row and you can plant columns 3 (or 4, if you insist) wide.
xxx xx xxx
Silver can (column can be longer)
xxxxxxxxx xxxxxxxxx xxxxxxxxx
With a golden/mystrile can you can plant crop areas 6 wide
With the blessed and mythic cans your reach is much longer and you could plant a crop on every square of any of the farmland areas, and be able to reach any of them from somewhere with your fully charged watering can.
Knowing how long it takes for most crops to grow helps. Also keeping in mind where you plant crops helps as well (for example, planting outside near the Waterfall decreases the average crop growth by one day, but I wanna say growing in town increases it by one day?).
Farmland = normal crop growth, and asde from Cher's site, you can find this info in your bookshelf. In-game, in your house. There is a book called crop growth, listing the various crop growth times, very handy.
The areas by the waterfall and the excavation site are -1 days to normal, the secret waterfall cave field -2 days and the areas in town are +1 day.