There's two big options for me: the 4-3-3 that we played against Arsenal, with Coutinho and Henderson in front of Gerrard and Sterling wide. But we also played that against Swansea with a real openness, we'd want to play the version against Arsenal where we concede possession in exchange for the rapid countering. Or there's, as PoP said, the diamond to clog things up in the middle. I think the game for me there would depend on Sterling (or Coutinho) manipulating space.
For me, I'd be inclined to the former, Coutinho is perhaps more effective at home at least in terms of his passing game and I'd want him in the side in a central position. But it's a risk, I can see the temptation to go with Lucas/Allen in a diamond and maybe have Sterling/Coutinho as a sub option.
City are very good, a well rounded team with a good attack. But we matched them well away and home advantage tips this to us. In many ways I think Chelsea turning up to spoil us will be more difficult.