With the idea that medieval man was uneducated and brutish comes the stereotype that medieval man had no manners, or at least, no manners beyond basic, crude conventions. This a surprising sentiment for the period that gives us the word “courtesy.” However, the Middle Ages has left us with dozens of etiquette books for both adults and children, some even declaring that “Good manners always make good men.” 
Courtly life was extremely ritualized, relying greatly on standards of etiquette. Many conventions are similar to today’s standards. I’ve listed a few of the most common conventions below. However, since many books focus largely on table manners, I will reserve those for their own entry.
Etiquette books frequently mention that if one needed to correct the misbehavior of another, it should be done in private, not in public.  This shows that people paid careful attention to the manners of others and often found it necessary to correct faulty behavior. Attention is given first to greetings: when entering one’s lord’s place, he should greet all present with a polite greeting, walking in at “an easy pace” (not rushing or dawdling), and if appropriate, kneel before the lord. 
Books stress that one should take care to speak politely—that is, to direct the content of one’s speech to pleasant topics, avoiding those likely to give offense or arouse anger.  When speaking, one should look the person being addressed in the eye, not letting one’s eyes wander about the room, and listen attentively when spoken to.  This advice is given both to those of lower rank being spoken to by those of higher rank, and vice versa.
Since etiquette books focus greatly on table manners, not as much advice is given to behavior outside of dining time. Most attention is given to content of speech, the content of which should be pleasant so as not to offend or arouse anger in others. As for physical conventions, leaning against things (the book specifically says “a post”) was impolite, as was sitting before being asked to do so.  Finally, as today, one should not handle the household decorations.  Along with expectations of polite behavior comes the command that it is a “passing foul thing” to be drunk.  As misinformation abounds about how much alcohol was drunk during the Middle Ages and movies tend to portray dinners as full of drunken ribaldry, this convention may come as a surprise to some.
The handkerchief was not invented until the late Middle Ages. However, one’s nose should always be kept clean. The preferable way was to use a cloth, but etiquette books note that peasants may be able to get away with using a sleeve, a practice appalling to upper classes. Erasmus notes that it is unacceptable (for both classes) to use hands for this purpose.  Etiquette books also mention that blowing one’s on the tablecloth, or even clearing one’s throat at the table, was a serious offense.  Hands should be kept clean with particular attention to fingernails.  Scratching, in general, was impolite.  Spitting was usually frowned upon , though some books mention that spitting is acceptable as long as one does it out of view of one’s fellows.
Rocking or moving around in one’s chair was impolite, not because of the action itself, but because it “gives the impression of constantly breaking or trying to break wind.”  I have plenty of records about the etiquette of flatulence in the Middle Ages, but I really don’t want to entertain the base factor by going into detail. I’ll summarize with this: it was thought that bad smells spread disease, so it was best to take care of business in private. Public bodily noises of all kinds were usually denounced, even those we would consider quite innocent today, such as a cough or clearing one’s throat. 
When speaking of medieval manners, I often get the impression that many expect to find something surprising in the etiquette books. Most conventions really haven’t changed. Medieval manners were, as today, expected to be rigidly observed in formal situations, while in casual situations, they could be relaxed as the situation demanded. For more information, simply pick up any piece of medieval literature and pay attention to how the characters behave.
- Rickert, Edith. The Babees’ Book: Medieval Manners for the Young: Done into Modern English from Dr. Furnivall’s Texts (London: Chatto and Windus, 1908). 13.
- Elias, Norbert. The Civilizing Process: Sociogenic and Psychogenic Investigations (Hoboken: Blackwell Publishing, 2000), trans. Edmund Jephcott, ed. Eric Dunning, Johan Goudsblom, and Stephen Mennell. 69.
- Rickert, The Babees’ Book, 3.
- Elias, The Civilizing Process, 69.
- Rickert, The Babees’ Book, 3.
- Ibid., 4.
- Wedgewood, Ethel. The Memoirs of the Lord of Joinville: A New English Version (London: John Murray, 1906). 10.
- Elias, The Civilizing Process, 49.
- Ibid., 56.
- Rickert, The Babees’ Book, 13.
- Ibid., 4.
- Ibid., 57.
- Elias, The Civilizing Process, 71.
- Rickert, The Babees’ Book, 57–58.