The Legend of Zelda: Skyward Sword Cheats

Amber Relic - Found almost anywhere. They are found very common in the Faron Region. You only need 20 of these for all the upgrades. (Eh... meh. Who cares about this thing.)

Ancient Flower - They can only be found in the Lanayru Region. They can only be collected if you trigger the Timeshift Stones. You only need 8 of these for all the upgrades. This includes fixing Scrapper that Lanayru Robot, which only 1 is required. (Pretty flower.)

Bird Feather - The birds can be found only in the Faron Region and you are required using the Bug Net (or the Big Bug Net). You will need to walk carefully towards them and snatch them if you are close enough. The Big Bug Net is highly recommended since it is in fact larger and easy to catch both bugs and birds. You only need 5 of these for all the upgrades. (Boring feathers.)

Blue Bird Feather - Same as the Bird Feather in the Faron Region, but the only thing is that the blue birds are quite rare. If you happen to see one, don't just run after them. Do the same method for the Bird Feather and you'll harvest some Blue Bird Feathers. You only need 5 of these for all the upgrades. (Blue as the sky!)

Dusk Relic - Like Amber Relic, but are in different color. These things can be found almost only in the Silent Realms. So be sure to take a peek at every corner while you are in the Silent Realm. Be sure to pick up many of them as possible. You only need 13 of these for all the upgrades. (Ooh... mysteriously pretty.)

Edit: If you are in the Silent Realm, the best way to harvest as many of them as possible is to get hit by the Guardians and start all over again. You will notice that the Dusk Relics you found will re-appear in the same location. This will reduce your time of harvesting, but you will still need to complete the trail in the Silent Realm. But either way, it's all about patience.

Eldin Ore - Found in the Eldin Region mostly. They are commonly found by digging those digging spots and treasure chests in dungeons. You only need 6 of these for all the upgrades. (These rocks or metals are boring.)

Evil Crystal - These things are hard to come by, but they can be harvested from Cursed Bokoblins in the fourth dungeon. But as long you have the Treasure Medal, it makes harvesting a lot easier. You only need 3 of these for all the upgrades. (They... don't look like crystals to me.)

Edit: If you recall the time where those Cursed Bokoblins were about to get you on the lone rope and there's an escape route above,...