Since I don’t like to use the mouse while coding, I usually
- move the cursor over the method
- type ctrl+k clrl+t to open the Call Hierarchy window
- move down to Implements node.
- type Return to go to the selected implementation
AFAIK this is the quickest way to find the implementation of a method, without ReSharper.
(By the way: you can use the same system to move from a class method implementation to the corresponding interface declaration: just select the root)