currently I'm thinking about how to implement a game loop. it should be possible to activate and to deactivate vsync. how do I implement the game loop so that my application cooperates with the vsync? Do I have to set special flags while initializing the ID3D11Device object?

At the moment my application runs a while loop and processes the message queue. after processing the message queue I call methods in order to update my game logic and draw my objects. should I be aware of being in time with my update and draw algorithms?

Since Direct3D 10 you need to use IDXGISwapChain::Present to get your back buffer on the screen. This function get the sync interval (0 = no vsync) as first parameter. Therefore it’s pretty easy to make it switchable.