For a seeker of Hinduism, an understanding of the meaning and significance of the sacred lunar days is useful to understand how this ancient tradition links the spiritual practice with rhythm of the cosmos. Ekadashi, Purnima, and Amavasya are the three kinds of lunar phases that stand out from each other and undergo a unique process of soul experience and practice in benefits. 

The Lunar Foundation 

The calendar follows in Hindus are primarily lunisolar based on the astrological preposition of two zodiacs-the solar seasons and the ephemeris or lunar phases in a year. Every month of a lunar calendar is divided into two fortnights: waxing period (Shukla Paksha) with growing moon and waning period (Krishna Paksha) with diminishing moon. Among these, three days are very special when compared to other sacred days:  

Ekadashi: The eleventh day of each fortnight (occurs twice monthly). 

Purnima: The full moon day concluding the bright fortnight (once monthly). 

Amavasya: The new moon day concluding the dark fortnight (once monthly

Ekadashi: The Day of Spiritual Discipline

The emphasis of Ekadashi is on devotion for Lord Vishnu and by personal attempt of purification. ``Among all days, Ekadashi is most dear to Lord Vishnu. Who observes Ekadashi fast with devotion, he gets merit as if he has performed a thousand sacrifices.''-Padma Purana (Uttara Khanda, ch 20 verse 8). Really, it may be:

Key Distinguishing Features:  

Twice a month occurrence.(24 in total per year) Fasting from grain and beans formation is the main spiritual exercise, Unearned by any association except with Lord Vishnu, Spanning Specifically Individual Spiritual Discipline  

The Skanda Purana (Chapter 10, verses 22-24) states: "Ekadashi is like a boat that helps the devotee cross the ocean of material existence. It purifies one from the subtle effects of past actions and creates conditions for spiritual progress." Purnima: The Day of Fulness and Grace 

Purnima is the epitome of divine energy, the moment when the barrier separating the two worlds of matter and spirit becomes so thin, it merges to the point of disappearance. It pronounces this statement: "As the moon reaches completion on Purnima, so too can the devotee experience complete divine grace through proper worship"-Matsya Purana (Chapter 141, verse 52). 

Key Distinguishing Features: 

Occurs once monthly (12 main Purnimas per year). 

Associated with plenty, fullness, and divine light. 

Celebrated with people in honor of a particular deity or event based on the month. 

Showcases constant celebration with the community and externals of devotion. 

The Devi Bhagavatam (Book 11, Chapter 23, Verse 18) states: "At the time of the full moon, Divine Energies flow freely towards Earth. That wise one who engages in spiritual practice on this day receives manifold blessings."

Amavasya: The Day of Connection with Ancestry and Renewal

For most traditions, Amavasya marks the darkness from which new creation is sprung and ancestral connection, traditional connections. The water offered to the ancestors on this day of Amavasya keeps them satisfied for a month. No other day equals Amavasya for ancestral offerings.-Garuda Purana (Preta Khand: 8;11)

Key Distinguishing Features:

Occurs once within a month (thus, there are twelve Amavasyas per year).  

Associated with ancestors, rebirth, and potential.  

Centered around the idea of pitru tarpana (sacred offerings to ancestors).  

Focuses on letting go, introspection, and starting afresh.

Markandeya Purana explains: "What looks like darkness during Amavasya is the seed of new creation. The wise one uses this time to let go of what is complete and prepare for what is emerging."

Philosophical Interconnection

These three sacred days represent different aspects of the spiritual journey. The Brihadaranyaka Upanishad (5.5.1-2) uses the moon as a metaphor for the soul: "The self waxes and wanes like the moon, but its essential nature remains unchanged." These three observances help practitioners come to terms with that unchanging part amid constant change.

In terms of what each day signifies regarding spiritual work: 

Ekadashi: Self control and devotion (sadhana)  

Purnima: Celebration and abundance (utsava)  

Amavasya: Remembrance and renewal (smriti)  

Best Practice Adoption for New Practitioners

For the newcomers to Hinduism, these observances are very valuable as they teach how to regulate one's life spiritually in everyday life:

Start with Purnima: Full moon is most easily seen; it has traditionally been associated with joyous celebrations rather than hard disciplines. 

Add Ekadashi: Once one has settled in learning to observe Purnima, add trying to observe one Ekadashi each month with a simple fast but increased devotional practices. 

Add Amavasya: Finally introduce Amavasya practices and, of course, remembering ancestors in one's contemplative activities.

 The Bhagavad Gita (17:14) reminds us how to offer: "Austerity of the body is fasting, simplicity, and purifying self-discipline and non-violence." It teaches the observance should be done in the right intention and within one's capacity. 

 Conclusion 

This quote from Bhagvat Purana epitomizes all Hindu rites in a way very pleasing: "True worship is that worship which awakens aware consciousness of the abode of the Supreme Lord in the heart of all beings."  

By knowing and keeping Ekadashi, Purnima, and Amavasya, seekers become involved in a living tradition which connects their individual spiritual practice to the rhythm of the cosmos, their family lineage, and the divine present. All these observances give not mere ritualistic chores but gateways into deeper dimensions of consciousness and connection, being highly resourceful practices for anyone sincerely exploring Hindu spirituality.