I believe Vaastu says that every home entrance should have a proper threshold. This can be done in wood or marble since it will absorb all the negative energy while taking in the positive energy for passing it throughout the house. The main door should be decorated with divine and auspicious symbols including the Cross/Swastika/Om, whichever works for you. Rangoli works on the floor also since it is known to invite good fortune into the home and is regarded as highly auspicious. There should be proper lighting for the main door in the evenings. Do not have any mirror directly opposite to the main door.