If you cannot eat a certain type of food or have some special needs, tell your host several days before the dinner party.
If you are a guest, it is polite to wait until your host starts eating or indicates you should do so. It shows consideration.
Always chew and swallow all the food in your mouth before taking more or taking a drink.
Always say thank you when served something. It shows appreciation.
You may eat chicken and pizza with your fingers if you are at a barbecue, finger buffet or very informal setting. Otherwise always use a knife and fork.
When eating rolls, break off a piece of bread before buttering. Eating it whole looks tacky.
On formal dining occasions it is good manners to take some butter from the butter dish with your bread knife and put it on your side plate (for the roll). Then butter pieces of the roll using this butter. This prevents the butter in the dish getting full of bread crumbs as it is passed around.
In a restaurant, it is normal to pay for your food by putting your money on the plate the bill comes on.