Turning engine to TDC

[jriewer]

I'm going to be changing my waterpump on my 87 420sel and see that Ive got to turn the engine to top dead center. Can someone tell me how to turn the engine and how do I know when its TDC?

Thanks

27mm socket. line up tdc mark on damper with pointer on waterpump. mark lower pulley with crayon or paint at tdc so its easier to assemble.