1 South Node and North Node.

The Moon Nodes are always exactly opposite in the chart.
The South Node (also called Ketu) represents the energy coming from our past lives, or from our family/ancestry/genetic inheritance.. It is an energy we are familiar with and needs to be balanced by the opposite energy of the North Node.
The North Node (also called Rahu) represents where we are called, where we will gain the greatest satisfaction...provided we dare taking up the challenge and step out of the South Node comfort zone.
The Nodes are placed in opposite signs and houses as well. The meaning of the Nodes in houses is equivalent the the placement in the analog signs, for instance:
my South Node is in Aquarius and in the 8th house. My North Node is therefore in Leo and the second house.
My karmic path in sign is from Aquarius to Leo, and in house from the 8th to the 2nd, which is equivalent to a Scorpio to Taurus path. (As Scorpio is the 8th sign of the zodiac and Taurus the second)
General meanings of the karmic paths.
Symbols are like magicians' hats: there is always more you can draw out of them. So whatever you can read will never be complete... however, roughly:
From Aries to Libra (South Node in Aries, North Node in Libra)
You are assertive enough, and maybe too much (Aries) Work on creating harmony with a partner (Libra)
From Taurus to Scorpio.
You know the value of life on earth and enjoy it. You may have become a little bit too attached to things or people. Learn that nothing is permanent and find deeper values.
From Gemini to Sagittarius
You know a lot, you communicate a lot, you adapt to circumstances. You may have become a bit too scattered and lost. Find meaning and coherence, knowledge and wisdom, unity.
From Cancer to Capricorn
In Cancer you belong... to a family, to a tribe, to a nation. Your sensitivity and emotional ties are strong. You may be too dependent on others. Break free from these ties, walk your own path. Take responsibility.
From Leo to Aquarius.
You are used to shine, you express yourself... or your ego. You give. It's time to learn to be a member of a larger group, a community, a city...without necessarily being the leader at all times.
From Virgo to Pisces.
In Virgo, you have paid attention to all necessary details. You serve. You're rational and efficient. It's time to remember the spiritual dimension.
From Libra to Aries.
You may have been compromising too much... You know how to maintain balance and harmony, but maybe the price you paid was too high. Claim your right to exist as an individual!
From Scorpio to Taurus
You've been confronted with the deep, dangerous, dark side of human nature. You've survived, you are a bit scarred though. Re learn to enjoy life on earth (I call this path the "post traumatic path)
From Sagittarius to Gemini
You've been seeking knowledge, wisdom, meaning. You may have become a bit dogmatic. Come back from theory to practice, communicate with people, adapt to circumstances...
From Capricorn to Cancer.
You are used to be responsible, important, successful. It's time to remember emotional needs, home, family, imagination, sensitivity.
From Aquarius to Leo
You have loads of ideas, you are a bit of a visionary, you belong to the great human family... It's time now to take centre stage and shine as a unique individual.
From Pisces to Virgo
You know the infinite worlds where there are no boundaries. You may be a mystic, a poet, possibly a scapegoat or an addict... Come back down on earth, become a little bit more skilled and rational and give your dreams some reality...
These interpretations are very general. I will never insist enough: the meaning of the astrological symbols can't be summarized in a few lines. The more we understand them deeply, the more we will be able to refine our interpretations.
2 The Regents of the Nodes
To know more about our karmic path, we need to look at the "regents". I'll give just an example: My own karmic path goes from Aquarius to Leo. Uranus is the planet that rules Aquarius. Therefore this planet, its placement in sign, house and its aspect will give more information about my karmic past.
The Sun is the planet that rules Leo, similarly, the position of the Sun in sign and house, along with its aspects, will tell more about what I'm called to do in this life.
My karmic path in house goes from the 8th to the 2nd. The 8th house is analog to Scorpio (the 8th sign). Pluto rules Scorpio. So Pluto in my chart will give more information about my past.
The second house is analog to Taurus (2nd sign) Venus is the planet that rules Taurus. Therefore, Venus in my chart, along with the Sun, talks about what I am here to do..
3 Black Moon Lilith
Black Moon Lilith is a very special energy. Through the sign and house, possibly aspects It points out an area of life where we have an ambiguous attitude, a craving for absolute perfection and possibly a rejection of the values associated. It can also show values that we may find sexually attractive. Its position will confirm or precise the challenges we are going to meet on our karmic path.
4 Special cases
When planet are conjunct to a node, they add there energy to the karmic path. For instance, if Mercury is conjunct to the South Node, it's energy is part of our karmic inheritance, and need to be balanced.
When a planet is square or semi square to a Node, it's energy is problematic. It can turn against ourselves, until we learn to master it better and use it as our best asset.

5 Pluto. If we follow Jeff Wolf Green, we can also look at the house position of Pluto for an area of life undergoing transformation and the polarity point (opposite) for what needs to be developed.