To me, it’s important to remember that Poseidon was honored during the late moths of the year, between December and January, in a time the ancient Greeks called Poseideon, after the God, Poseidon. His feast day was celebrated in the beginning of winter; some accounts claim the 8th day of December as his while others claim his day was closer to the winter solstice.
Traditionally, honoring Poseidon involved sacrifice and prayer, yet in this day and age it is far too difficult and even illegal in some cases to offer the traditional animal sacrifices (black bulls, as I’ve found most cited). Instead, let’s offer the Sea Lord gifts relating to other aspects of his.
Pine is considered sacred to Poseidon, and is heavily used during these holiday months. Burn pine incense or hang fresh pine boughs in your home. Along with the pine tree, the ash tree is also considered sacred to him; consider making a wand or talisman using these woods and decorate them with other symbols pertaining to Poseidon, such as shells, the trident, horses and dolphins. Display statuettes of his sacred creatures in your home.
I once read that a small manner of sacrifice in his honor would be to fill a bronze or copper bowl halfway with water and then place a figure of a horse inside; in effect sacrificing the image of the horse in his name.
It is still suggested to recite the Orphic Hymn 16 or the Homeric Hymn 22, both of which are listed below. Feel free to add a personal touch by writing your own poems or prayers and speaking them aloud for him.
Hear, Neptune [Poseidon], ruler of the sea profound, whose liquid grasp begirts the solid ground;
Who, at the bottom of the stormy main, dark and deep-bosom'd, hold'st thy wat'ry reign;
Thy awful hand the brazen trident bears, and ocean's utmost bound, thy will reveres:
Thee I invoke, whose steeds the foam divide, from whose dark locks the briny waters glide;
Whose voice loud founding thro' the roaring deep, drives all its billows, in a raging heap;
When fiercely riding thro' the boiling sea, thy hoarse command the trembling waves obey.
Earth shaking, dark-hair'd God, the liquid plains (the third division) Fate to thee ordains,
'Tis thine, cærulian dæmon, to survey well pleas'd the monsters of the ocean play,
Confirm earth's basis, and with prosp'rous gales waft ships along, and swell the spacious sails;
Add gentle Peace, and fair-hair'd Health beside, and pour abundance in a blameless tide.
I begin to sing about Poseidon, the great god, mover of the earth and fruitless sea, god of the deep who is also lord of Helicon and wide Aegae. A two-fold office the gods allotted you, O Shaker of the Earth, to be a tamer of horses and a saviour of ships! Hail, Poseidon, Holder of the Earth, dark-haired lord! O blessed one, be kindly in heart and help those who voyage in ships!