Here are the first 10 hints:
/TODO/ Intro ...

1. It's more about listening than it is about dancing.
2. There are three steps (just three): forwards, backwards and sideways.
3. There are two roles: leader and follower.
4. There are three Tango rhythms: the Tango (classical), the Milonga and the Tango Waltz; the "New Tango" or "Tango Nuevo" can also be seen as a separate branch.
5. Tango is usually danced in a ring, following (and respecting) a counter clockwise direction.
6. The embrace is arguably the most important feature of the dance. It can be open or closed.
7. Most of the time, Tango dancers have all their weight on one foot, whose choice is not (entirely) random.
8. There is (surprisingly) such a thing as a "basic step", or "basico".
9. There are two dancing systems - parallel and crossed.
10. There are many great teachers of Tango touring the world, from which you can learn new tricks.

And now the explanations:

1. If this were possible, I would advise a person willing to learn how to dance Tango to listen to Tango music at least two months before taking the first steps. Find more about the music here. Here are some of the most well known composers and artists, to whose music you will surely dance at some point, if you go to Tango parties:

• Carlos Gardel
• Carlos di Sarli
• Anibal Troilo
• Juan d'Arienzo
• Osvaldo Pugliese
• Rodolfo Biagi
• Edgardo Donato
• Francisco Canaro

There are of course many others, but this should get you started. Nuevo tango authors include Otros Aires, Gotan Project, Narcotango, or Bajofondo. The most famous modern age tango author is arguably Astor Piazzola.
When we think of the typical tango orchestra, this can include violins, bass /cello, piano and a special instrument called "bandoneon". Not all composers rely on the same instruments to illustrate the theme of the melody and the rhythm. Likewise, not all dancers follow the same instruments to perform their steps. However, usually, after about a month of listening, you should be able to accurately mark the measure of any tango piece of music. At that point you should start to feel a certain meaning in your steps, that will stick to you from then on.
This "meaning" will be enhanced by your teachers during the Musicality lessons, and of course, the further entries of this blog should help.

2. The "three steps" paradigm says the following: a teacher will rarely, if ever, try to teach you schemes and sequences of steps, leading to a certain choreography. Argentine tango is neither taught, nor learned that way. Every trick you will learn in tango can be taught to a sufficiently skilled follower at first sight. And this is in fact the goal of each tango lesson: to teach the leaders how to propose a step and the followers how to go with the lead.
In order to make the connection between these 3 possible steps, you will sometimes need the forth element: the pivot. This is not a step "per se", it is a simple turn to the new direction, and it is performed on the toes of one foot.

3. Continuing the "three steps" paradigm, let us explain briefly the relationship between a leader and a follower. Tango is a form of communication, a game between two partners - one tries to send a message containing the "intention", the other tries to understand and perform the intended step. The channels through which this message is sent are multiple (and no, they do not include speech :D). The hips, the upper body and the arms of the leader are some of these channels. Actually seeing them with your eyes is optional.

4. The Classic Tango is the first rhythm taught - it has 8 measure phrases, with a clearly marked beat, making it excellent for a beginner's practice as well as for an advanced dancer's degree of freedom.
The Milonga (a style which shares its name with the common Tango party) is a fast rhythm, in which every beat corresponds to a step. A Merengue dancer for example will be quick to grasp this idea.
The Tango Waltz, or Creole Waltz is a tango rhythm that shares much of its musicality with the Austrian waltz (or quick waltz), while being still played (and danced) in Tango steps. The three step sequencing plays an important role, still.
The New Tango is a never ending source of innovation, because it essentially imports, transforms or tunes other music styles into tango. Jazz, Chillout, Hip-Hop or Trance are just some of the sources that can be recognized in Nuevo.
Being played in a rather open (and common) musical system, you can fathom tango steps on a wide variety of music - and you might have the surprise to see your teachers dance argentine tango while listening to Gorillaz.

5. As a traditional rule, Tango is danced counter clockwise, with the mind clearly set to respect the other dancers' space. The responsibility for these goals rests entirely with the leader. Most of the time, the leader will walk forwards and the follower will walk backwards. Since dancers rarely have the luxury of leaving the center of the ring empty, they should tend to occupy the outermost space first. Also, the dance direction refers to the general movement, it does not forbid the dancers from going against it occasionally (and briefly), if the space allows such a maneuver.
A follower wearing high pointy heels can be a devastating (and completely innocent) weapon.

6. Many teachers will present the embrace as technically the most important feature of the dance. I would add that it is probably the most important feature socially as well. Unless you actually like dancing with a partner in your arms, you probably will not enjoy Tango.
The embrace is the embodiment of the relationship between partners. It should be carefully kept during the entire dance - and this is a shared responsibility of both partners.
There are two classes of embrace: tight and open. The tight embrace gives the follower the best access to information about the lead, but it also severely limits the couple's degree of freedom. It is suited (e.g.) for the Milonga rhythm, where the steps are fast but rather small. The open embrace gives the couple a lot of freedom to perform wide movements, but the connection is less firm and thus less evident.
The dance will start with one embrace, but that can be changed at leisure during the song, usually during certain tricks or moves, to make it fancy or aesthetic.

7. As we noted before, Tango is danced as a game of interpreting "secret" messages sent from the leader to the follower. But the dance is not random, each step depends on the previous one. If the two partners simply walk, facing each other, comfortably (i.e. leader left foot forward, follower right foot backward) and one partner skips or misses one step, they will bump into each other at the first chance they get. That is why the leader must know which of the follower's feet holds his or her weight (and consequently which is free to move next). The manner in which the leader acquires this precious information is not by looking at the follower's feet. It's simpler (and faster). The leader decides which foot is free. So, among the first things a leader learns in Tango is to set and keep track of the follower's feet. And among the first things a follower learns in Tango is that he or she should only change the free foot when the message comes to do so.
On top of that, none of the partners should tarry with their weight on both feet.

8. The "basico" consists of 8 steps in the following sequence (from the leader's point of view) - leader starting with his weight on the left foot: 1. back, 2. left (apertura), 3. forward on the outside of the follower, 4. forward, 5. change of weight on the spot leading a cross to the follower, 6. forward, 7. right, 8. change of weight on the spot. There are 8 steps and since most Argentinian teachers show this sequence, it has become so familiar that during seminars you will often hear them call the left sidestep "the two" (dos) or the follower's cross "the five" (cinco) - referring to their respective order in the "basico". The "basico" and its variations encompass a significant part of the Tango.
It is surprising that such a sequence exists, because nobody teaches sequences in Argentine Tango. This is perhaps why it is the only 8-step sequence worth mentioning.

9. In Tango, a dancing system is one of the two ways the partners can walk relative to each other - e.g. left foot to right foot, or left foot to left foot. Obviously, the first system in the example (i.e. the parallel system) is the easiest, because it is the natural way of walking while facing each other. However, we find ourselves quite often in the situation illustrated by the second system in the example (i.e. the crossed or "crusado" system). Walking straight while in this system can be a difficult but quite useful exercise. We can change systems at any time during the dance - the easiest way to do that is to have one of the partners change their weight, while the other doesn't (an extra step or a skipped step - remember, these are always performed on the intention of the leader)

10. Although the Golden Age of Tango is long gone, the movement is far from dead - in fact it is thriving. So, as soon as you get the hang of walking ("caminar"), as well as a few more easy tricks (which you will call, most likely "cross", "ocho", "giro" and "rebound") - you should go ahead and look up the Tango workshops held in your area (or, depending on your budget, across the globe). Some of the best teachers you should be keeping an eye on (and this is certainly subjective) are: Gustavo Naveira and Giselle Anne, Sebastian Arce and Mariana Montes, Murat and Michelle Erdemsel, Javier Rodriguez and Andrea Misse, Adrian Veredice and Alejandra Hobert, Ozhan Araz and Serkan Gokcesu, Pablo Villarraza and Dana Frigoli, Alejandro "Lucho" Lucero and Cecilia Piccinni.

Hopefully this is not too much information all at once. If you have anything else to add or you disagree with some of the information above, feel free to comment.