Informal service is what you are typically expected to do in the Den when serving the free. It is exquisite and beautiful, but perhaps not quite as showy when serving individuals, and simply not efficient when serving at a gathering.
Casual service refers to times when you may be called upon to simply refill or fetch something without fanfare of any sort. This is commonly called for when those who you are serving are busy with other things and do not wish you to take extra time with formalities, or, perhaps, when you are out with your owner on a trip or some other situation where expedience is more important than appearances.
When we speak of formal service, it can refer to extra formal individual service, but more often refers to service at formal dinners, banquets or other events. While feasts tend not to be formal events, they are included in this category as well, although the protocol will usually differ a bit from, say, a banquet.
Certain things are going to be the same across the board with any gathering. One of these is, of course, that there are generally more people to serve than slaves to go around.
This makes individual service impractical, so, rather than going to fetch individual foods and drinks, slaves will circulate with botas, pitchers, platters, and the like, offering food and drink to each attendee.
When there are multiple slaves available to serve, each slave will usually be assigned specific items to serve throughout the event, perhaps trading off at times with other slaves. When there are fewer slaves, of course, a slave will often be required to serve several courses or dishes in a row.
Den slaves may be rented to serve at anything from a family friendly wedding feast, to a wild orgy, so much will depend upon the specific event.
Here are some general guidelines, however.
Formal Dinners/Banquets
Formal dinners or banquets will generally have specific separate courses, served in order, and will be more organized affairs.
More often than not, slaves will be expected to be nearly invisible at a formal dinner party or banquet, much like servants in the Victorian era, waiting in the wings with watchful eyes and "magically" appearing only when needed to refill a drink, serve the next course, clean a spill or take away used dishes.
When serving from platters, tureens, serving bowls and such, as you will almost always be doing at any large gathering, you should always serve from the left side of the person you are serving.
The main reason for this is that most people are right handed. So, for example, when a slave must use his right hand to serve from a platter, it is least intrusive if he stands to the left. This way, the platter can be held safely away from the diner as the slave leans forward to reach his/her plate. And, in the case of placing side dishes, it makes most sense to put them to the side that is less in focus, leaving the right side free for the main dish.
Wine and all other beverages are presented and poured from the right. This is logical, as glasses are placed above and to the right of the guest's plate, and trying to pour from the left would force the server to reach in front of the guest, which is, of course, unthinkable!
When each course is finished, the used dishes and any garbage should be cleared from the right of each guest.
You should wait until all guests have finished with a course before removing the first dish. Just as the ideal of service is to present each course to the entire party at once, it is best to clear the plates at the same time, too.
It has become common for servers in some establishments to remove plates as each guest finishes, in violation of this rule of serving etiquette, perhaps because it can be interpreted as extreme attentiveness on the part of the waiter. Nevertheless, the rule holds firm. The most elegant service calls for the removal of all dishes at the end of that course. There is nothing more irritating than to have a plate removed from under you while you are still chewing your food. Not only should you wait, but you should also give some time between courses. Food should not come out as soon as one course is finished. The idea here is to make a nice evening of the affair, and multi-course meals should take hours!
Feasts
Feasts can certainly be very formal affairs, after a fashion, but tend to be less formal seeming, at the very least.
A feast is more likely to have attendees serving themselves, from large platters on the tables, and almost always will involve more drinking than more formal events!
This does not mean that you will not be serving, but rather, that the service will differ from that at, say, a banquet.
In addition to bringing platters out to the tables, slaves will circulate with additional platters of various side dishes, deserts, drinks, and the like.
Keeping guests' tankards and drinking horns and such filled will be a big priority, and there is more likely to be impromptu entertainment of various sorts, such as wrestling, dancing, and other slave sport.
While something like throwing a slave on the table and taking him/her would never do at a formal dinner, such things are often commonplace in feasting halls.
Also, attendees will tend to be more scattered about at a feast, rather than all gathered around the tables in an orderly fashion.
When offering food and beverages, unless at a more "chaste" event, it should be understood that the slave is offering him/herself, as well.
Be sure to make that clear in your tone and body language, but do not ever force yourself on a free person. It is not your place.
The most you may do is beg for use if your needs are upon you, and the desires of the free are always top priority, whether they desire your flesh or simply a drink refill.
Parties/Festivals
Parties or festivals, like feasts, may be quite formal in some respects, but are unlike a formal dinner, though many are preceded by a formal meal.
At such gatherings, there is no real central seating area, as with a meal. Guests are scattered about, sitting, standing, reclining, engaging in activities, etc.
Serving will be done by circulating with food and drink, and offering it to attendees.
As with feasts, there may well be slave sport and cavorting during a party, depending on the type, and slaves will usually be understood to be on offer along with food and drink.
