1 - The Silent aren’t a species, they’re a religious movement.
2 - They can alter your mind without you knowing it, for you forget all about them after you saw them. Well, if those ARE the silence.
3 - The Church is at war with the Doctor, for reasons unknown. Not only The Church as in Catholic Apostolic Church, but many denominations such as Anglican, the Headless Monks, etc.
4 - Amy got pregnant in her wedding night, in the tardis, during the flight. The girl, Melody Pond, was kidnapped by the church representative, Madame Kovarian, and trained to kill the Doctor. She’s partly a time lord and can regenerate. Her last regeneration uses the name of River Song.
5 - You can make a flesh avatar and they’ll have all thoughts, emotions and etc of a ‘real’ person. The tardis stabilizes them even when they’re still in the first stages of development.
6 - The Doctor died, in Lake Silencio, at 5:02pm. He invited the others to meet him at 4:30pm. That’s 32 minutes before his death.
7 - Voice interface says the Doctor will die in 32 minutes after Melody poisons him.
8 - Voice interface says regeneration isn’t an option. The Doctor starts to regenerate when shot by the astronaut.
9 - The astronaut suit is able to feed, keep alive and mostly do anything for a person. Quite like pandorica.
10 - River/Melody killed the Doctor.
11 - River/Melody was the child regenerating in the end of 602; latter she went to leave near her parents and got them together. They named their child after her.
12 - Melody poisons the Doctor with the poison of the judas tree. It didn’t seem to affect her much, but the voice interface says there’s no cure.
13 - The Doctor is wearing a weird coat in the begging of LKH. He chances his clothes twice.
14 - The Doctor comes into the room where he’ll die wearing the same clothes he wore in Amy and Rory’s wedding, more specifically, when he’s in the tardis in the end. In the beginning, he had a red flower on this suit that is missing latter. He has a balloon in his hand, as those seem in the wedding/stag party.
15 - The Doctor that says he’s 1102, before being shot, isn’t wearing his normal clothes AND doesn’t seem to have a tardis around.
16 - The was a flesh!Doctor. It/He died, but the Doctor believed it could survive.
17 - The Doctor says that “a lot more happened in 1969 than anyone remembers”, in TiA. He’s trapped in 69 during Blink.
18 - River’s first appearance in the show was in an episode called “Silence in the Library”. By the time he was to deliver the script, Moffat had already been invited to become main writer and executive of the show.
19 - The Tardis exploded and caused cracks in the skin of the universe. We don’t know why it exploded.
20 - Silence will fall when The Question is answered. The not-vampire in Venice says she saw Silence, and also everything goes silent in the end of that ep. Prisoner Zero also knows about it.