I hadn't thought about it until a few days ago, either. I didn't stop to think about how gestures like kissing might actually be very important to a culture.
In my northernmost country (Country A), I've decided that kissing is generally seen as sexual or romantic, except when done with family. And when done with family, you don't kiss on the mouth. People may kiss the hem of the king's robes as a sign of loyalty and piety. I decided to do this with Country A because this is where my main character begins, and I wanted their customs to be most familiar to my readers, so I went with the customs of kissing I myself was raised with. Additionally, kissing is also done between knights before and/or after a duel or joust, to demonstrate that there are no hard feelings-- which usually works out well, because a lot of these knights know each other and are good friends.
With werewolves, it's a little different: kissing, licking, touching the mouth is seen either as begging or a gesture of supplication. They depend heavily on context and the body language of both participants to know the intent of the kiss. If one werewolf is in wolf form, he may kiss the other to beg for mercy or favor. In human form, he'll reach up with his hand to touch his chin-- a concept that was greatly inspired by this. Most of their romantic/sexual kisses are accompanied by other forms of affection, such as braiding another's hair or giving foot-rubs.
In the more southern countries, it's quite different. Country B is very standoffish when it comes to kissing, so you only kiss someone in private if you're family, or you only kiss their hand as a gesture of respect for your liege. Kissing in public is seen as inappropriate, especially by the upper classes-- it's often viewed as trashy and a sign of being low-class. The upper classes like to pretend they never kiss, but of course, behind closed doors... heh.
In Country C, even royalty are accustomed to being kissed on the cheek by those close to them-- personal servants, dear friends, family. They'll return the gesture with the latter two, but expect to receive it by the former. To be kissed is to be shown a certain amount of affection, deference, and respect, all of which you would expect to receive from those three categories of acquaintances I've listed.
Country D is also much the same as Country A, with some elements from Country C. Many of them will kiss statues of their god to demonstrate religious reverence, and will kiss their dogs for much the same reason. You can only receive a non-sexual kiss of greeting or friendship from someone who is of your same caste-- unless you initiate it with someone of a lower caste first (i.e: king kisses his advisors, who are one-caste below him.) The person of the higher caste gets to initiate it on his own terms, as it's a sign of friendship and respect, and people of lower castes don't get to demand that.
