HOW TO ENTER
Enter or leave your house or office with your right foot first, as it was the tradition of the Prophet Muhammad 
. Imam Abul Ala Hasan ibn Ahmad al-Hamazani, a great scholar of hadith of his time, was so keen on applying this sunnah to the extent that if someone entered his house with their left foot first, he would ask them to go out and re-enter with their right foot first.
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When entering or leaving a house, do not push the door violently or slam it shut, nor leave it to close by itself. Close the door quietly with your hand. You may have heard a hadith reported by Muslim wherein Aisha 
, may Allah be pleased with her, quotes the Messenger of Allah : Gentleness adorns every act. Its absence will tarnish it.
ENTERING WHILE OTHERS ARE ASLEEP
Be quiet and gentle if you enter a place where people are sleeping, whether during day or night. Be considerate; do not cause any undue noise when entering or exiting.
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Muslim and Al-Tirmidhi reported that the honorable companion al-Miqdad ibn al-Aswad said: “We used to keep for the Prophet his share of milk, and when he would come at night he would greet us with a voice loud enough for those awake to hear, without disturbing those who were asleep: In addition, whenever the Prophet used to pray at night, he would recite the Quran with a voice that pleased those awake, without disturbing those who were asleep.
GREETINGS
When entering or leaving your house, acknowledge those inside by using the greeting of Islam: Assalamu Alaykum wa Rahmatul Allahi wa Barakatuh (peace, mercy and blessings of Allah be upon you). Do not forego this Islamic greeting by saying something else such as ‘Good Morning’’ or ‘Hello’. This greeting of peace is the sign of Islam and the phrase that the Messenger of Allah recommended and used. The Prophet taught his faithful servant Anas ibn Malik to greet his family when entering or leaving his house (Al-Tirmidhi). Qatada ibn Diama al-Sadusi, a prominent tabi’in (successor) said: Greet your family when you enter your house. They are the most worthy of your greeting.” Al-Tirmidhi reported another hadith wherein Imam Nawawi in al-Majmu said: “It is preferred to say Bismillah arRahman arRahim (In the name of Allah, Most Gracious, Most Merciful) when you enter your house or the house of others. You should say salaam even if you enter vacant or uninhabited places and Al-Tirmidhi and Abu Dawud narrated a hadith by Anas that should be said when entering:
ANNOUNCING YOUR PRESENCE
When entering a house, make your presence known to those inside before you approach them. Avoid startling or frightening them and do not descend upon them suddenly. Imam Ahmad ibn Hanbal said: “When a person enters his house, it is recommended that he makes noise by clearing his throat or tapping his shoes.
SEEKING PERMISSION TO ENTER
If family members are resting in their rooms, and you want to join them, it is appropriate to ask for permission or knock on the door. Otherwise, you may see them in a condition that you, or they for that matter, may dislike. This applies to the entire household: immediate family or otherwise.
KNOCKING AND RINGING
Knock at the door, or ring the doorbell in a pleasant way and not louder than is necessary to make your presence known. Do not knock loudly and violently or ring the bell continuously Remember that you are a visitor and not a thug raiding the house and frightening its occupants. Likewise, Al-Bukhari reported in al-Adab al-Mufrad that the companions of the Prophet used to knock on the door of the Prophet with the tips of their fingers. This soft and gentle knocking, or ringing, is appropriate for those whose living quarters are close to the door. For those living further from the door, it is appropriate to knock on their door, without banging, or ring the bell loud enough to enable them to hear it.
Leave adequate time between two knocks or rings. This will enable those performing ablution, praying, or eating to finish without making them rush. Some scholars estimate this interval to be that of the praying time of four rakaats. Keep in mind that a person may have just started the prayers before you rang the doorbell.
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After three knocks or intermittent rings, you may feel that the person you came to see is busy, otherwise he or she would have answered you. If this is the case, then leave as mentioned in Al-Bukhari and Muslim.
While waiting for permission do not stand in front of the door. Instead, stand to the right or to the left. The Messenger of Allah upon coming to someone’s door avoided facing the door directly. Instead, he would stand to the right or the left of the door.
REPLYING TO ‘WHO IS IT?’
When knocking on the door you may be asked: ‘Who is it?’ Identify yourself, using your most common name but do not respond with: ‘It’s me’, or ‘somebody’, or ’Guess who?’ ‘These words are useless in identifying who is at the door. The Prophet discouraged one from saying: ‘It’s me’ because it does not reveal your name. Al-Bukhari reported that Jabir ibn Abdullah said: ‘I came to the Prophet and knocked on his door and he asked: ‘Who is it?’ I answered: ‘It is me’ and the Prophet disapprovingly said: ‘It is me, it is me.’ For this reason, the companions used to mention their names whenever they were asked: ‘Who is it?’