What should I wear? If I'm married, do I bring my spouse? What if I'm a man with multiple wives? Do I bring any kind of gift or dish? Where should I sit? What kind of food will there be? What should I talk about - and what shouldn't I talk about? Should I try to talk to Suleiman at all, and if so, what are the rules to address him? Where do I stay when the dinner is over?
If you were an official you would be required to wear clothing fitting of your stature, including but not limited to highly specific turbans, kaftans, and even colors. Certain colors were limited to Muslims, Jews, Christians etc..
Spouses were not brought, such gatherings were oftentimes seen as fitting only for men. That of course depends on the ocassion. Sometimes Sultan or his Mother would organise prayer banquets, in which women may be present.
The seating position would be shown to you, and would be highly influenced by your position and importance. More important people were closer to the Sultan in seating arangements.
The gift would be expected, especially if you are a foreigner. The recorded gifts from Crimean Girays to Ottoman court mostly composed of Ermine Kaftans, embroided and embelished saddles, ornate and highly decoraded swords as well as bows.
If you're talking with Sultan the rules are simple, dont speak unless spoken to, and keep your eyes and head low. Sadly, you wouldn't have much initiative in the choice of topics. Your's is to follow if you can in whatever topic Sultan choses to discuss. That changes if he is your friend. If you were Ibrahim Pargali, then you would talk to him like any other man, but with respect of course.
If it is a longer banquet, like a wedding, which could take several days, rooms would be provided to you within the palace, if you are of suficient status.
Source: History of Turkish-Ottoman empire by Joseph von Hammer.
It depends on your job/title and the motive behind the dinner. The concept of having a dinner with Sultan Suleiman is a bit of a stretch. If you were an official outside of his inner circle, you wouldn't be talking to him at all.
Salomon Schweigger who was hired as a chaplain by Habsburg ambassador to Istanbul, wrote that officials had to sit with their counterparts during banquets (He traveled to Istanbul in 1578, 12 years after Suleiman's death).
Sultan [Murad III, Suleiman's grandchild] ordered his servants to serve dishes. Pashas and ambassadors were sitting cross-legged on the floor. Sultan's position allowed him to see every single guest, but guests couldn't see him clearly. (...) We were seated outside of Diwan room. No ordinary table, just a floor table. Rice, lamb, fried chicken and a pigeon-esque bird.
Scheweigger explicitly portrayed dishes, drinks, guests etc. I couldn't find the English translation, but here's the original text: http://digitale.bibliothek.uni-halle.de/vd17/content/pageview/7529876 Chapters III & IV from second book. (Page [118] 55)
Philippe du Fresne-Canaye, an official hired by French ambassador to Istanbul (François de Noailles), portrayed the exact same scene (in 1573).
Venerable Ambassador, first and second pashas Mehmed and Piyale were sitting at a silver table. Ahmed Pasha, Zal Pasha, Mustafa Pasha were seated at a different table.
Having a dinner with Suleiman the Magnificent is not realistic. Only exception would be işret meclisi.
If you were a famous artist/scholar (poet, musician, philosopher etc), you could be invited to his private party; bezm (بزم) or işret meclisi (مجلس عشرت). İşret meclisi was completely different than other feasts. It represented a combination of earthly pleasures (fine dining, wine, weed etc), artistic excellence (poetry, music, calligraphy etc) and intellectual curiosity (historical texts, mythological legends etc). Sultans were indulging themselves with işret meclisleri, which were held at Sultan's private gardens or elegant pavilions in Topkapi Palace (Suleiman's parties would be soberer though. A pretty sizable percent of Ottoman Sultans had no problem with drinking alcohol. Suleiman wasn't one of them. He was also a quasi-monogam). If you were lucky enough to get invited to an işret meclisi you could interact with him in a less formal way.
As mentioned in another reply, the sultans from Süleyman onward typically ate in private. Süleyman attempted to build an aura of majesty by severely limiting his public appearances, such that he would only be visible during highly orchestrated ceremonies meant to broadcast his splendor. It was difficult even for the highest officials of the empire to have direct access to his person. Thus, Süleyman would appear in public for a meal with petitioners and soldiers only once a year, on one of the two major Muslim religious holidays (ʿÎd-i Fıtr and Kurban Bayramı).^1
The historian İsmail Hakkı Uzunçarşılı describes the nature of the ceremonies that took place at that time, based on narrative sources and state documents. According to him, the sultan would appear in the Arz Odası, located just beyond the entrance of the third courtyard (soldiers and dignitaries were located in the second during the feast). There he would be met by the state dignitaries, and they would kiss the hem of his garment and/or his hand. Upon being greeted by the higher ranking officials, the sultan would rise to his feet, while he would remain seated for the lower ones. After this process was complete, he would rise again and be applauded before departing to change his outfit and then to depart with a procession to Haghia Sophia for prayer. Upon the sultan's return he would be greeted by the Grand Vizier, who would then depart to eat with the other state dignitaries while the sultan returned to his private chambers for his own meal.^2
Even should the opportunity arise, there would be no talkıng with Süleyman whatsoever. One important element of the imperial facade was the near-complete silence of the sultan. He would speak little if at all during public appearances. The Habsburg ambassador records an audience he had with Süleyman in the mid 1550s, in which Süleyman spoke only a single word to him: "güzel".^3 As for what one would talk about with the other officials at the dinner - it's hard to say. Political topics were certainly not off-limits. İbrahim Peçevi records an anecdote in which he and his superiors discussed the status of the Safavid frontier while at a banquet in the 1620s.^4
Gifts were frequently given to other dignitaries rather than the sultan, unless one was a foreign ambassador. Hezarfen Hüseyin Efendi records the course of the imperial celebrations (sûr-ı hümâyûn) of 1675, in which Hadîce Sultan, the ~17 year old daughter of Mehmed IV, was married to the high-ranking vizier Musahib Mustafa Pasha, followed by the circumcision of the imperial princes Mustafa and Ahmed. As for gifts, here's an example of those given to a prince:
"On behalf of Prince Ahmed:
From the governor-general of Cyprus: five silver water-cups, five silver mugs, five silver trays, four units of Persian silk cloth, four units of satin cloth, four Hatâyî [Chinese cloth?], four units of Indian cotton, four turbans."^5
I only give one example because the other officials offered very similar gifts - perhaps they planned it out ahead of time, or their gifts were determined according to custom. Either way, he sure ended up with a lot of cups and mugs by the end of the celebrations. Officials of lower status naturally offered smaller gifts. Members of the religious hierarchy frequently offer books as well, and several of Istanbul's guilds are recorded as delivering gifts of their own high quality products.
What's the food like?
How far out from Istanbul would invites go? Delegates from Europe or China? Japan?
Did Suleiman give any banquet favors like jewelry to his guests?