Silver Keys can be found in various places in all Albion, just waiting for the Hero to find them. Their main purpose is to open Silver Chests. You'll mostly have to fish for them or dig them out of the ground as they are mostly found inside flowery circles, or in water where ripples can be seen.
This Silver key is located in the clothing shop, the first building on the left as you enter. To obtain the key in Bowerstone South, enter the shop and head upstairs. Go out to the balcony to find the key.
This Silver key is located in some ripples in the water in Fisher Creek. To find the ripples, go behind the fisherman's house. Fish off the bank at the ripples near the chest. The second ripple from the right has the silver key. 
This Silver key is located in a large ring of flowers slightly south-west of the Rose Cottage. The ring of flowers is to the left of the house, or to the right if you are exiting the houses interior. 
This Silver key is located inside a large glowing stone on the southern end of Darkwood Lake. To obtain it,aim and fire an arrow through the hole at the top. This will knock the key down for the Hero to collect. Or you could use enflame level 3+
This Silver key is located in a dig spot in Memorial Garden. To obtain this key, dig beneath the axe wielding statue.  This key will also be obtained in the course of the Treasure of the Ghost Pirate bronze quest, but can be retrieved beforehand (although doing so will cancel the quest).
This Silver key is located in a ring of flowers by a chest in the southeastern part of Twinblade's Camp. Look for the makeshift tavern by the lake. The chest and Silver key should be behind the big tree to the left. 
This Silver key is located in a ring of ferns in Knothole Glade. The ring of ferns is found between two houses in the southern part of the village, by the southeast corner of the buyable house. The key is buried in the centre of the ferns. This is the same circle of ferns that the White Balverine retreats to during the second encounter looking for the Hunter's Wife. 
This Silver key is located inside the Bowerstone Manor bedroom. Search the bed to obtain the key. In Fable, this key can only be obtained if the Hero marriesLady Grey. In Fable: TLC and Fable Anniversary, exposing Lady Grey's crimes and becoming mayor of Bowerstone will also grant access to this location. NOTE: Exposing Lady Grey means that you won't be able to access the Demon Door by the Grey House.
This Silver key is located in some ripples in the water in Headsman's Hill in the small pond outside Headsman's Cave.  This small section of the region can only be reached when battling Thunder during the Mayor's Invitation quest, but can also be accessed after by using the demon door you used to exit that area. However, it is possible to glitch down to the area. Near the ledge where you fall off fighting Thunder, there is a chest. Stand as close to the left side of the chest as you can, then use your Guild Seal to teleport to another location. After that, recall back to Headsman's Hill. You should now be just in front of Headsman's Cave.
This Silver key is buried in a ring of mushrooms, found on the Northern edge of the Cliffside Path map.  (Not to be mistaken with The Clifftop Path which is west of Oakvale. This is on the path through Bargate Prison. Enter through the crypt.)
This Silver Key is located inside a cabinet within the lighthouse of Hook Coast. To obtain it in Fable and Fable Anniversary, the Hero must either pick the lock on the door to the lighthouse or smash it down, earning evil points. In Fable: TLC, however, you must go to the top of the lighthouse and can get the key then.
In Fable: TLC and Fable Anniversary, a Demon Door in The Necropolis requires all Silver Keys obtained by the Hero as payment to open, leaving the Hero with none. This can be avoided by obtaining no keys before talking to the door, who will still open.
With at least one key in your inventory, an exploit can be used during quests to obtain unlimited silver keys using the Hero Save. On any quest where you find a Silver Key (such as the Graveyard Path quest, which has three), obtain the key(s), Hero Save, and then replay the quest. Then obtain the key(s) again and repeat. Players on Fable will need no more than 20 Silver keys and players on Fable: TLC and Fable: Anniversary will require all 30 keys to unlock all Silver Chests
In Fable Anniversary, due to changes made to the save system, this exploit is no longer possible. Each key must be found individually.