Culture

Usually people make some sort of an altar for one or many deities, and place offerings to a deity by marking the offering and placing it infront or on the altar of the deity they wish to gift it to.

(not confirmed): Some people prayed to their gods by writing the symbol of their god on one side, and a request on the back before putting it into a box. Others may have prayed directly to a symbol or sculpture of their god, usually also presenting an offering.

January 19 — Great Watercrossing 

January 28 — Domovoi's Day

The beginning of February — Veles's Days

February 2 — Gromnitsa: Winter Holiday of Perun

February 21 — Day of Stribog 

February 24 — Fat Thursday

March 2 — Kikimora's Day

March 3 — Yarilo-Ovsyannik

March 7 — Maurice 

March 4/17 — Gerasim Grachevnik

March 21 — Marzanna's Day

March 9/22 — Soroki

March 31 — Ladodeniye

April 1 — Domovoi's Awakening

April 7 — Malesnica

April 14 — Clean Thursday

April 14/27 — Voronets

April 16-21/22 — Rusalii 

April 22/21 — Lelnik

April 23/24 — Yarilo’s Day

April 30 — Meeting of the Five

April 30-May 2 — Dozynki

Last week of April-first week of May — Radonica

May 9/10 — Day of Mother Earth 

May 28 — Green Week

May 30 — Zmeynik

July 2 — Berehynya’s Day

July 7 — Kupala's Holiday

July 20/August 2 — Perun’s Day

July 19/August 1 — Mokridy

August 14/19/29 — Spasy

September 23 — Ryabinnik

Fall Equinox — Expressing Gratitude for the Harvest

October 1 — Shipovnitsa

October 23-30 — Dziady

October 31 — Veles’s Night

November 1 — The Day of Svarog

November 12 — Chickadee’s Holiday

November 30 — Andrzejki

December 6 — St. Nicholas Day

December 21 — Winter Solstice

December 25/January 7 until January 6/19 — Svyatki 

On march 21st, or 4th sunday of Lent before easter, a Marzanna Doll is made, usually out of straw and shaped like a human, and dressed. After this the doll is usually set on fire and drowned (being set into the river and sent to coast away). The drowning of the doll is meant to summon spring.

This practice is also included during the spring equinox for Rodnovers

March 2nd
A Kikimora is a spirit

"Kikimora (pronounced Kih-kee-mora) is a female house spirit from Slavic lore who can be helpful or malevolent depending on the behavior of the homeowner. In differing versions of her stories, there are two kinds of spirit, one generally helpful and the other hurtful, both depicted as a woman sometimes with a chicken’s beak or duckbill." (Joshua J. Mark, Worldhistory.org)

"A kindly kikimora who approves of how the house is kept will pitch in and help with the work, only causing trouble if people are lazy and fail to keep order. If one wishes to rid oneself of a kikimora, the surest way is to keep a home so clean she gets bored and leaves; this belief inspired women to be diligent about housework. Similarly, children were taught that the kikimora was attracted by noise at night and so they should be quiet and go to bed when told or a kikimora would take their breath, give them terrible nightmares, or take them away; this encouraged an orderly nighttime routine." (Joshua J. Mark, Worldhistory.org)

March 31 — Ladodeniye.
Lada, the Goddess of Love and Peace

"People used to celebrate Lada’s festival with lively games in her honor, making it an integral part of their springtime rituals." (mythlok)

There is an entire ritual procedure including materials to gather in preparation for it on Urban Druid, you can visit the site by clicking/tapping  on the button on the right that says "Urban Druid: Lada"

"Kupala Night, also known as Ivanа-Kupala, was a summertime holiday traditionally celebrated on the shortest night of the year in June. The practice includes a number of Slav rituals, opposed to the winter holiday Koleda." (S.14)

On July 20th or 21st, a festival which usually incorporates a feast, as well as games or activities including Tug of War for example.

"People celebrated this important festival at the end of the summer as a way of greeting the upcoming season. This time represents a shift in the forces from feminine to masculine. 

Perun represented the highest deity, worshipped by many in Slav Europe. He is the lord of the sky and lightning, comparable to Zeus in Greek and Thor in Norse mythology. 

People celebrated the festival by offering sacrifices and gifts at this time to win over his good spirit in the upcoming autumn season. A sacred bonfire was often lit and protective amulets were consecrated. Men later wore the amulets in times of war. 

Warriors commonly showed off their warfare skills and crafts. At the end of the festival, men performed a custom representing a fight between the lord of the heavens and Veles. The duel always ended with victory for the god of lightning and thunder." (S.14)

"Mokridy is an East Slavic holiday that occurs on July 19 or August 1. This holiday falls into a similar category of holidays as Kupala Night or the Drowning of Marzanna, which is that of honoring gods and performing rites in the name of ushering a good harvest or a new season. Mokridy specifically is a set of rites performed by communities and families that may include bathing in blessed water, women performing rituals to either summon rain or banish it, the creation of specialized moytanki (referred to as Mokredina for invoking a dry spell, Sukhoveyka for invoking rain) which were also used to adjust the course of weather. This holiday has been most studied as it has been performed in northern Russia, according to most ethnographers, though it is believed to have been practiced in different forms in other spaces. For example, there are notations of Ukrainian women in the 19th century performing a mokrida ritual where they would throw pieces of kudel into a well before starting their weaving.
Sources (all of these are in Russian I'm so sorry there's literally only a facebook post from a good creator on this topic that is in english) "
-Bolotnitsa
(sources Bolonitsa used are below)

"The Autumn equinox in Slavonic culture and religion represents the beginning of the harvesting season. This time is celebrated with the Harvest festivals (Rodogosch or Tausen) and it ends with a celebration dedicated to the great goddess of the Earth." (S.14)

Dziady is a holiday to honor the dead. Dziady is held twice a year, once in spring and another in fall. "Early Slavs believed souls returned from the underworld of Nawia (or Nav), during certain times of the year, and the end of October was one of those times. This celebration with the spirits of the afterlife took place in graveyards, where great fires were built to provide light for the deceased and for them to warm themselves. " (Source 15, Brendan Noble). Usually a feast is held, but also food was gifted to the dead, by placing the gift on their graves. "The giving of sacrificial blood as well as clothes and food such as kasha (a type of porridge), eggs, honey, and even vodka was meant to offer ease to the souls as they make the difficult travel to Nawia. While Nawia was considered a positive afterlife, the journey to it is difficult (which I talked about more here)." (Source 15, Brendan Noble)

A major part of the festival held during Dziady, was the guiding of ancestors back to Nav, which included dances around fire, as well as wearing Karaboshka masks, usually made of clay or wood. When Dziady is coming to an end, people would leave out gifts for the dead, and offerings to other spirits without families while they hold torches. (check out Brendan Noble's writing, they do a great job and go more in-depth than I did!)

"Koliada or koleda celebrates the beginning of the pagan yearly cycle. Essentially, koleda is a pre-Christan, New Year celebration that takes place on the winter solstice in December." (S.14)

"A springtime holiday usually celebrated in March, Komoeditsa paid tribute to the Bear god. People would commonly offer food (usually a type of thin pancakes) by leaving portions in the forest." (S.14)