The greeting postures you refer to are part of the customs prevalent among people, and those customs may be acceptable in Islam if there is no violation of the rules of Shari`ah such as considering such acts as a form of worship. Thus, any action that is similar to an act of worship is forbidden in Islam when it is offered to anyone other than Allah.
Sheikh Muhammad ibn Al-Mukhtar Ash-Shanqiti, president of the Islamic Association of Lubbock, Texas, US, states the following: “People have different traditions in greeting and expressing respect, including kissing hands and nose and standing up for the newcomer. All these traditions might be acceptable if three conditions are met:
1. They cannot be taken as a form of worship;
2. They cannot be exaggerated and overdone;
3. They cannot include something that has been forbidden by the Shari`ah, such as a man touching or hugging a woman that is not his mahram.
In addition to this, we should judge every situation within its own circumstance. For example, the Prophet (peace and blessings be upon him) is reported to have said to his companions: “Do not stand for me the way the Persians do with their kings.” At the same time, it is reported that he asked his companions to stand up for Sa`d ibn Mu`adh saying: “Stand up for your leader.”
The difference between the two narrations is that in the first case people used to worship and adore their kings, in which case the Prophet blocked avenues that would mean any sense of worship to other than Allah. On the other hand, Sa`d (may Allah be pleased with him) was brought injured (in the battle of the Trench) to the Prophet, so the Prophet wanted to honour him and boost his morale. So, the difference is in the circumstances that surrounded each case.”