Before removing the cylinder head, it is necessary to depressurize the fuel system, and separate the cable for the negative terminal on the battery. Pull the radiator and evaporator and the water pump and drain The inter cooler and expel the 
Exhaust Manifold/heads. Subsequently, take out the 
Timing Belt or 
Timing Chain from the 
Camshaft sprockets and extract the camshafts. Remove all the sensors and hoses you can, and finally, undo the cylinder head bolts with 1/4-turn intervals to the point where they can be easily removed by hand along with their hardened washers; do not remove the M6 bolt at the front of the cylinder heads on the 2006 and later models. Remove the cylinder head from the engine block, it's also recommend to use wooden block with hammer and should apply extra caution not to bend the head while lifting from the block as this might cause damages to the gasket surface. Lastly, for inspection, with the help of a precision straight edge run it across the gasket surfaces of each head and measure the clearance to make sure it falls within the standard limits; the areas should also be checked for cracks and coolant leakage. Before tightening, make sure the contact surfaces of the cylinder heads and block, are free of the old gasket material by scraping with a gasket scraper soaked in brake cleaner. Admiral the corner edges as well for indentations, peening, nicks, and /or scratches; whether minor or significant, the file/machining should adequate. Using a tap run the threads in the cylinder head bolt holes and blow clean with compressed air. Remove small dirt or whatsoever from the bolts, and if any of the bolts is found to be stretched or rusted must be replaced. Simply line up the new gaskets to the dowel pins in the block, aligning them correctly, then apply RTV seal as recommended. Place the head gently onto the block in a manner that does not compromise the gasket; you should apply clean engine oil on the thread of the bolts to be tightened. Loosen the bolts as stated then in the recommended sequence and finally tighten the bolts to the torque that has been recommended excluding the small one at the front of the cylinder heads. To recap, undo the removal operation, fill the cooling system, change the engine oil and filter as well as start the engine and ensure, any leaks are rectified.