'Namaste', or its more formal version 'namaskar', is difficult to translate directly. It roughly means ‘I greet the god in you’ or ‘What is holy in me greets that which is holy in you’. The most beautiful translation we have heard is ‘I honour that in you where the whole universe resides’.
The namaste is not normally executed in combination with a bow. Indians do not really bow, except when showing deep respect. It is acceptable just to meet the hands in ‘prayer’ before the chest and keep the head upright, while saying ‘namaste’ or not saying anything.
A guest in India is always given hospitality. It is a duty to do so, since the guest is considered a god or godly being.