Here is a nice recent example of how to defend against the London System.

Telljohann,Sven (2423) – Adams,Michael (2725)
1.Nf3 d5 2.d4 Nf6 3.Bf4 c5 [D02]
Tradewise Gibratar Chess Festival 2013 (2.1), 23.01.2013

Position 1
White is nowhere close to organizing an attack on the kingside which gives black some freedom to choose plan. What do you suggest for black?

• ..Nf6 and then ..Ne4 if allowed. 
• …f6 and prepare to break in the center with …e5 
• ..h6 and wait to see what white is up to first 
• Something else 

Black to Play