...Nc6 and ...Qb6
London System
1.d4 d5 2.Nf3 Nf6 3.Bf4 c5 4.e3 Nc6 5.c3 Qb6 6.Qb3 c4 7.Qc2 Bf5
Black develops the knight and then hits b2 with the queen; after Qb3, Black gains space with ...c4.
Practice this lineThe idea
After 4...Nc6 5.c3 Qb6 6.Qb3 c4 7.Qc2 Bf5, Black has gained space on the queenside, and the bishop on f5 hits White's queen. Kiril Georgiev's book on the London argues that delaying Nf3 avoids this line.
Plans for White
Move the queen out of the bishop's line and complete development with Nbd2 and Be2. Then look for e4 or b3 to break up Black's queenside space. White's pieces still have their usual squares, so the setup is slowed, not broken.
Plans for Black
Keep the queenside space with ...b5 and ...b4 if useful, develop with ...e6 and ...Be7, and castle. Trading the light-squared bishops leaves White short of attacking pieces.
Watch out for
For White, the pin on the diagonal. After 7...Bf5, the queen on c2 is attacked, and leaving it there can cost time or material.
For Black, overextending. The c4 pawn takes space but can be undermined by b3 or e4 if Black's pieces aren't ready to support it.