The guest should immediately notify the host if he has no intention of eating there for some reason or the other. It should not happen that the host prepares food and then all goes to waste. This will cause much grief to the host who underwent inconvenience and laboured to make hospitable arrangements for the guest.
The guest should inform the host of his whereabouts so that the latter (host) does not have to search for him when meals are ready to be served.
The guest should not accept anyone's invitation without the consent of the host.
The guest should not interfere in the arrangements and system of the host. However, there is nothing wrong if the host assigns an arrangement or an act to the guest.
The guest should never adopt a demanding attitude or tone. He should tender his wishes with humble request.
If the guest is on diet, he should inform his host immediately on arrival. Some persons exhibit ill-manners in this regard at the exact time of eating when the food has been served.
The guest should not ask the host for something, for perhaps the host is unable to fulfil the request and is thus put to shame. (Necessities are excluded.)
The
guest should leave a little food over so that the host does not think that maybe the food was not enough and the guest has not eaten sufficiently. This will put the host to shame. (This does not mean that the guest should leave some of the food in his plate
uneaten. He should clean the plate with his fingers. This is
Sunnah 
. Some food should, however, be left in the serving utensils.)
Do not accompany an invited person to his host's residence. The host, merely out of shame may be constrained to ask you to remain for meals while in actual fact he has no intention of doing so. This causes difficulty to the host. Some persons very quickly accept such instant invitations which are made by coincidence. The host may feel belittled if he does not ask you to remain for meals.
Do not inconvenience the host nor put him to shame by making a request at the time of departure. The time for fulfilling your request may be too less and the host will suffer shame by not being able to satisfy the guest.
If several varieties of food are served, the guest should taste a bit of every variety. This is a right which the host has over the guest. However, if the guest is ill or on a prescribed medical diet, then this will be an exception.
Do not initiate an intricate topic while eating. The talk should be light, otherwise the pleasure of the food will be destroyed. While eating, the greater part of one's attention should be directed to the food.
It is not permissible for a guest to give any food to a beggar or anyone else (i.e. from the food which the host has served). Similarly, if so me food is presented in a utensil, it is not permissible to eat from the utensil. Remove the food into own utensil. However, if the form of the food will be destroyed by emptying it in another utensil, then it will be permissible to eat from the utensil in which it was sent, e.g. pudding.
When going to a place for some work, etc, and while there you go to meet an acquaintance, then immediately inform him of your staying arrangements so that he does not gain the impression that you are his guest.
The Ulamaa should be extremely careful when going to eat at the place of their host. They should not impose on the hospitality of the host by taking along with them a group of friends / students / Mureeds.