This was something I composed off the top of my head in a Nichiren Buddhist Forum. It reiterates the main points in recent entries.I have expanded it and corrected the most obvious errata.
I compare Buddhist contemplative practices to an elevator. A Buddhist Altar is like the door to the elevator. Or we could say the Altar is like the housing that marks a formal place where the door can be accessed; and the Gohonzon enshrined in the Altar is like the door? The Daimoku, chanting Namu or Nam Myoho Renge Kyo, is like a key that opens the door. The door leads to a mental state called Access Concentration. Some are content to sit outside the door and worship or pray to it; or ask for divine favors. There is nothing wrong with doing that; it is called Preparation Concentration. It takes courage to enter. Veneration and prayer are means to develop trusting faith, so we have the courage to advance.
However, for some, worship becomes the end, rather than the means to the end of developing trusting faith and faith with discernment. Others may actually enter the elevator car, and, perhaps, go for joy rides. They may not realize that the car goes places, that it stops at various floors. Of course, this ride is not meant literally. The elevator is a symbol for Access Concentration. Interesting things can and do happen in Access Concentration. Visions and messages are fairly commonplace; but not all experience them. Also, prana or pneuma 気 {shi, ki, qi} might flow through body. For example, one's posture might become straighter and the hands often feel warm. The Mandala Gohonzon used in Nichiren Buddhism might appear three-dimensional and glow. The paintings or statues of the Buddha and other beings enshrined in some altar arrangements might appear to come to life. Some could mistake these phenomena for more advanced attainments.
As I mentioned, the elevator of Access Concentration goes places. Others have visited these 'floors' and mapped them. There are nine main floors on one side. Collectively, these nine are called Fixed Concentration or Absorptions. As the car of Access Concentration approaches one of these floors; which are actually meditative states, there is a sinking sensation, just before it settles to a stop and the door opens, much like the odd sensation one feels on a physical elevator. When one gets off the elevator, and enters one of these 'floors,' or moves from Access to Fixed Concentration; one's five external sense doors close. One experiences no physical contact between the sense organs and their objects. If someone speaks to us, or taps us on the shoulder, it will take several attempts to get our attention.
In the first four of these, there is a perception of form in the abstract; mental imagery or intangible forms; but, as I mentioned, no sensory contact. The first of these four levels has five attributes -- analytical thought, rapt attention, emotional joy, vedanic bliss, and one pointed awareness. These gradually dissipate at the higher levels. At the second level, analytical thought and rapt attention are gone. At the third, there is only bliss and one pointed awareness. At the fourth, the one pointed awareness fades and merges with equanimity. These first four floors are called the Form Absorptions, or Fine Material Absorptions. Some may use other words; like Concentration, Meditation, or Contemplation, instead of Absorption; but it all means the same thing.
On the Fifth through Eighth Levels there is neither form nor contact; these states are completely abstract and purely conceptual. At the fourth of these, the eighth level overall. even conception and perception fade into 'Neither Perception nor Non-perception.' These four are called the Formless Absorptions, Fine material Absorptions, or Attainments. The Ninth is a cessation of mental activity, called Nirodha. Visiting any or all of these nine levels is variously called Calm Abiding Meditation, Stopping Meditation, Absorption Meditation, Concentration Meditation, Fixed Concentration, Samma Jhana, Samyak Jhana, or Samatha / Shamatha Bhavana.
There is only one floor on the other side; with four or five open rooms. It is really pretty much on the ground floor. In a sense, we are going through Access Concentration to the other side. There are different stages of this, but explaining gets rather complicated. This 'floor' is called Alert or Mindful Concentration. Unlike with Fixed Concentration, in Mindfulness or Mindful Concentration, the external sense doors remain open, so there is contact. The mind moves rather than remaining at a fixed point; but there is no attachment or clinging to sensory objects. The mind is discerning; but pliant, supple, and non-judgmental. As progress is made, there is an enhanced or purified sensory contact. One practice of this is called the Four Frames or Foundations of Mindfulness {Satipatthana, Smrti-upasthana}; another is an observation of the rising and falling of the five clinging aggregates or khandas / skandhas. There is also Nichiren style 観心 {kanjin}; among others.
Finally, there are Five mental states that absolutely keep us from experiencing anything more profound than a very fleeting Momentary or Vaporous Concentration. These are called Hindrances or Veils. Momentary Concentration is like catching a passing glimpse of the elevator. We must temporarily overcome the Five Hindrances, or lift the Five Veils, before we can move into Access Concentration. The Hindrances are:
1. Sensory Desires, lust, greedy carving, avarice, infatuations.
2. Enmity, anger, hatred, rebelliousness, resistance, closed mind.
3. Lazy Nature, boredom, melancholia, funk, mental fog.
4. Anxiety and Depression; unresolved guilt and shame.
5. Mistrust, distrust, cynicism, excessive skepticism.
Before we can enter the elevator; or move into Access Concentration, some preparation or preliminary exercise is very helpful. So there is also a third kind of concentration. This is variously called Right / Correct / Proper Endeavor / Effort / Exertion / Exercise {Samma Vayama, Samyak Vyayama}, Preparation / Preliminary Concentration, or the Fourfold Restraint. This helps us to at least temporarily overcome the Five hindrances and consists of:
1. Blocking or restraining mental afflictions that have not arisen.
2. Letting go of or abandoning mental afflictions that have arisen.
3. Cultivating merits or virtues.
4. Maintaining and suffusing merits.
Afflictions are just mental states that motivate bad behavior; like greed, hatred, ignorance, pride, envy, and so on. Merits are positive mental states; like kindness, compassion, patience, and so on; which motivate rightful conduct. Virtues are the inherent attributes of Buddha Nature. The various knots, afflictions, fetters, obsessions, etcetera, in the mind and heart, keep innate virtues from emerging or surfacing.
There are many long lists of afflictions to avoid and merits to cultivate. To keep it simple, cultivating merits and/or virtues really covers all four restraints. Positive mental states are like clean water; they block 'dirt' from entering, cleanse 'dirt' that is present, purify the mind, and suffuse blessings. The most popular merit cultivation right now is probably Loving Kindness Cultivation. This is also commonly referred to as Compassion Meditation. It breaks down into developing four wholesome mental states that serve as antidotes to common afflictions.
There is a silent "4 kinds of persons" kindness meditation that seamlessly blends with the fourth or even fifth prayer. The Tibetans have a method called Tonglen, but I am not very familiar with that. There is also a method of suffusing or radiating good will in the ten directions; which can be blended with sending people Daimoku / chanting Daimoku for others. This is a very powerful mojo to heal personal relationships, among other things. After I arouse the intangible states of Loving Kindness, Compassion, Joyful Empathy, and Impartiality or Equanimity, I visualize my Daimoku powering these emotions and then spiraling 'mettawaves' outward in a clock-wise direction. There is no need to mix in other mantras. The concept of cultivating impartial loving kindness is already contained in these words from Soka Gakkai's silent prayers, "I pray for peace throughout the world and the happiness of all humanity."
This is all easier than it sounds and is not all that time consuming. It gives me something to do during Gongyo, other than chanting for a new car or for temple closures. There is nothing wrong with chanting for things that meet our needs and wants. However, if we become obsessed with acquisition of material goods, or attached to momentary sensory pleasure; then our chanting can turn into cultivating the First Hindrance. Meanwhile, turning Daimoku into a curse, to get revenge, is obviously cultivating the Second Hindrance. Instead of trying to destroy real or perceived evil; it just might be better to generate and transmit healing metta-waves?