Kaminalara's summoning ritual

• Procure a 1 pound cube of pure salt. 
• Infuse this with two pints of the blood of a good-aligned creature and allow to dry brown. 
• Upon this place the profane symbol of the Demon Prince to be summoned, and into the center of this place a perfect Timmasc mushroom preserved in Mind Flayer brine. 
• A candle made from the fat of a sentient is burned, and a desecrated holy symbol of a good deity is blackened in the flame. 
• Then the fat drippings are poured over the mushroom and the symbol of the Demon Prince, and its common name is chanted. 
if the ritual is completed perfectly, even if you do not speak or know the Demon's true name, it cannot resist the summons.

The Demon Prince may be contained temporarily within a magic circle, or the summoner may protect themselves within such a circle, but the Princes are not long restrained by any mortal, and may escape to wreak havoc of their own desiring. Even if you are certain your summoning was prompted by them, their first order of business may be to destroy you, so take care to prevent your own demise.
Likewise, to keep them on the material plane, or the plane of your choosing, you may need to cast forbiddance or other spells to block their immediate escape. While minor demons are generally locked to a single plane - whichever one they happen to find themselves on or are summoned to - Princes travel the Astral and Ethereal with ease, and may use these as conduits to other planes. They may also decide to take you with them.
Lastly, by the use of multiple symbols, and multiple names, more than one prince may be summoned. What we have learned in communion with Our Lady Lolth, other lesser sentients have bastardized to invoke other princes for their own desires., and it is said that in summoning multiple princes, care must be taken to avoid having two together at one time in one place, as they detest the sight and presence of other princes more than anything else, with few notable exceptions:
Graz'zt, always sly, preening and prideful, prefers negotiations and battles of wits to fighting, and has bound other princes with oaths and threats of curses such that he may not be attacked - though they will seek to thwart him. Graz'zt is still more than a match for a mortal warrior, but understands Princely immortality makes fighting another prince somewhat pointless. 
Zuggtmoy and Juiblex are rivals, but also romantically linked; their relationship is chaos and certain madness for those who witness it. Nevertheless no term properly describes them, as lovers or anything else implying the capacity for love, or goodness, is horribly incorrect. They work together but also desire nothing more than the utter destruction of the other.
Lolth is counted among the Demon Princes but she is of course, of a different substance entirely, holding her own through sheer power and force of will in the same way Tiamat holds her place in the Hells without being diabolic in substance. Lolth may travel as she pleases among, and occasionally as one of, her people, and while much simpler invocations may be used to summon her - as simple as a polite mention of her name - she may choose to ignore such invocations as well as her attentions are fickle and her goals are obscure. This ritual will bring her without fail, but if she is unwilling to stay, the summoner will surely breathe their last in the utterance of her name.