When you first start farming you are given 5 tools to use: the Hammer, Hoe, Sickle, Ax, and Watering Can. With these tools you can clear the debris from your neglected crop field and plant some vegetables. The 6th tool is the Fishing Pole, which you have to receive from Zack. Go to his house on Mineral Beach during your first few days on the farm. He will find a Fishing Pole in among his stuff and give it to you. If when you visit him he doesn't give you the pole, make sure you have an empty slot in your Tools section of the rucksack. You can store your tools in the box inside of your farm house when you don't want to carry them around.
Listing of the farm tools
Each tool has an upgrade-meter that will increase with usage. When the meter reaches 100%, the tool can be upgraded to it's next level of power. You can see the upgrade-meter by pressing the Select button, then the Left directional button once. You will see all 6 of your tools listed and their usage percents.
When the tool is ready to upgrade, you will first need to have the appropriate Ore in your inventory. At the 100% mark, the tool's upgrade-meter will reset to 0% and a colored "dot" will appear under its name. The "dot" is the same color of Ore that you're going to need to dig out of the Spring Mine. Then take the Ore and your tool and talk to old man Saibara. He is the town's blacksmith and will upgrade your tools to the next power level for a small fee.
Once you have had your tools upgraded to level 5, the level 6 "cursed" tools will appear in the Lake Mine. Each of your tools has a cursed version of itself, which you can find by digging in the ground on certain levels of the mine. The cursed tools don't replace your existing tools; you can put them in your tool box and still have access to your level 5 tools. Cursed tools cannot be removed once they are equipped. You'll have to go to the Church and have Carter give a blessing on the tool to unequip it. He can give blessings when he's in his confession booth on Mondays and Wednesdays between 1pm and 4pm. Carter will also be in his booth when the weather outside is raining or snowing. When he casts a blessing on your tool, it will be removed from your equipped item slot and put back into your rucksack.
The benefit of owning the level 6 tools is that they are, by far, more powerful then your level 5 ones. The disadvantage is that they also suck up a lot of energy every time you use one. You might only be able to use a cursed tool five times before you turn blue! To counteract the energy consumption, you can work on getting the cursed tools permanently "blessed" by doing 1 of 3 different things.
When your cursed tools have all been transformed into blessed tools, the Mythic Stones will appear in the Spring Mine. You can find Mythic stones on the same mine floors you find the Goddess Jewels on. When you find a Mythic Stone you can have Saibara upgrade your level 6 tools one last time. Then you will have the ultimate level 7 tools and no more upgrades are available.
After your tool has been powered up, you can use it's extra strength by holding down the B button when using the tool. The longer you hold down the B button, the higher the tool's power level will be.