"Courtesy demands that you, when you are a guest,
shall show neither annoyance nor disappoint no matter what..."
No matter what the event is or how well the hostess has planned and prepared, success depends on enthusiastic, congenial and considerate guests.
A welcome house guest above all is ADAPTABLE. Be ready for anything or nothing at all.
As a guest it is not necessary to ever eat anything that goes against your morals or that you are allergic to. Proper etiquette says to NOT mention these in advance to your hostess so she doesn't feel obligated to change her menu. It is pretty hard to plan around everyone's likes and dislikes. Just avoid the items you cannot eat or choose not to. If necessary have a snack before arriving. If you know that you will not be able to eat anything being served you might discuss it with your hostess so she knows that you will be bringing a meal for yourself prepared according to your restrictions. A classic example of this would be an Orthodox Jew who requires a kosher meal. For family and close friends this can be more lenient. I know that when I first met my husband's family I would never have dreamed of mentioning my food allergy to anyone in advance for fear of making extra work for them. After the first time I avoided a certain food because of an ingredient in it, my sister-in-law noticed and over the years has begun to even read labels on foods before I visit so we can avoid a problem in the future. That's because she's a good hostess!
You may want to help your hostess, but avoid the temptation to chase her into the kitchen trying to help and then end up chattering away while she's trying to make her last minute preparations. Take your cue from the hostess. If you have offered to help and she has declined your help, don't insist. She evidently has a plan. She will always appreciate your offer though.
Conform to the habits of your hostess. If they are early risers, while you are their guest so should you be within reason. There is the chance that you are an early riser or unable to sleep in the late evening. Take a book with you to while away the time when perhaps your are awake and they are not. If you read one of your hostesses books during your visit, do not dog ear the pages and return it to its proper place before departing.
Never stay longer than originally planned. End you visit while you and your hostess are both having a good time.
Leave your room and bath as you found it. My sister-in-law says "Do NOT try to do something nice by stripping the bed for your hostess". She may not be prepared to do the laundry that day and would prefer to do these tasks on her own time line. But Emily post suggests you ask the hostess first and at the very least remove the sheets and fold them at the foot of the bed after pulling the spread into place to make the bed appear made so the hostess does not forget to change them. Use your best judgment based on your relationship with your hostess.
Don't forget your "bread and butter" gift for your hostess. My sister-in-law is the one person we stay with regularly. As close family, etiquette sometimes disappears depending on who all is involved, but I never ever forget to bring a bread and butter gift for her, a small token of my appreciation picked out just for her. It can be as simple as a bouquet of flowers or a box of candy, but should be something she will personally love.
Follow up your visit with a thank you note within a day or two.
What do you do special for your hostess?