Here is a systematized presentation of the well-known "20 Important Spiritual Instructions" of Swami Sivananda, and it enlarges upon the prerequisites required for the all-round discipline that should act as the forerunner to direct meditation, arranged in their sequential order.
Get up at 4. a.m. daily. This is Brahmamuhurta, which is extremely favorable for meditation on God.
Asana: Sit on Padma, Siddha or Sukha Asana for Japa and meditation for half an hour, facing the east or the north. Increase the period gradually to three hours. Do Sirshasana and Sarvangasana for keeping up Brahmacharya and health. Take light physical exercises as walking, etc., regularly. Do twenty Pranayamas.
Japa: Repeat any Mantra as pure Om or Om Name Narayanaya, Om Namah Sivaya, Om Name Bhagavate Vasudevaya, Om Saravanabhavaya Namah, Sita Ram, Sri Ram, Hari Om, or Gayatri, according to your taste or inclination, from 108 to 21,600 times daily.
Dietetic Discipline: Take Sattvic food, Suddha Ahara. Give up chillies, tamarind, garlic, onion, sour articles, oil, mustard, asafoetida. Observe moderation in diet (Mitahara). Do not overload the stomach. Give up those things which the mind likes best for a fortnight in a year. Eat simple food. Milk and fruits help concentration. Take food as medicine to keep the life going. Eating for enjoyment is sin. Give up salt and sugar for a month. You must be able to live on rice, Dhal and bread without any chutni. Do not ask for extra salt for Dhal and sugar for tea, coffee or milk.
Have a separate meditation room under lock and key.
Charity: Do charity regularly, every month, or even daily according to your means, say six paisa per rupee.
Svadhyaya: Study systematically the Gita, the Ramayana, the Bhagavata, Vishnu-Sahasranama, Lalita-Sahasranama, Aditya Hridaya, Upanishads or Yoga Vasishtha, the Bible, Zend Avesta, the Koran, the Tripitakas, the Granth Sahib, etc., from half an hour to one hour daily and have Suddha Vichara.
Brahmacharya: Preserve the vital force (Veerya) very, very carefully. Veerya is God in motion or manifestation - Vibhuti. Veerya is all power. Veerya is all money. Veerya is the essence of life, thought and intelligence.
Prayer Slokas: Get by heart some prayer-Slokas, Stotras and repeat them as soon as you sit in the Asana before starting Japa or meditation. This will elevate the mind quickly.
Satsanga: Have Satsanga. Give up bad company, smoking, meat and alcoholic liquors entirely. Do not develop any evil habits.
Fast on Ekadasi: Fast on Ekadasi or live on milk and fruits only.
Japa Mala: Have Japa Mala (rosary) round your neck or in your pocket or underneath your pillow at night.
Mouna: Observe Mouna (vow of silence) for a couple of hours daily.
Speak the Truth: Speak the truth at all cost. Speak a little. Speak sweetly.
Reduce your wants. If you have four shirts, reduce the number to three or two. Lead a happy, contented life. Avoid unnecessary worry. Have plain living and high thinking.
Never hurt anybody: Never hurt anybody (Ahimsa Paramo Dharmah). Control anger by love, Kshama (forgiveness) and Daya (compassion).
Do not depend upon servants: Do not depend upon servants. Self-reliance is the highest of all virtues.
Self-analysis: Think of the mistakes you have committed during the course of the day, just before retiring to bed (self-analysis). Keep daily diary and self-correction register. Do not brood over past mistakes.
Fulfil duties: Remember that death is awaiting you at every moment. Never fail to fulfil your duties. Have pure conduct (Sadachara).
Surrender to God: Think of God as soon as you wake up and just before you go to sleep. Surrender yourself completely to God (Saranagati).
Swami Chidananda writes, “Swami Sivananda gave us one aspect of His teachings in the form of the 20 Important Spiritual Instructions. These instructions comprise a harmonizing of the outer and the inner, the emphasizing of the inner and practicing of the teachings of the ancient sages and seers of the Upanishads, practicing of the teachings of all the saints who through the centuries have graced and blessed Bharatavarsha (India) by their ideal life and teachings. This practice, together with the normal life is Gurudev’s special teaching to the world, and summing up, the practical 20 Important Spiritual Instructions give us the key to Blessedness even while living in the world and through the world itself.
Excerpted from Twenty Important Spiritual Instructions by Swami Chidananda.