Copying from the old forum before it a splode. Where possible, I have aimed to separate fact from speculation.

Table of Contents

1. History
2. Age
3. Your character's past
4. Archetypes
5. Culture and social roles
6. Relations
7. Draenei factions and organizations
8. Draenei in Cataclysm
9. Common mistakes and misconceptions
10. Recommended reading

1. History

I won't go in detail into the detailed history of the race. It was outlined quite nicely in other guides, so here I'll only write the basic facts, a Cliff Notes that I would expect every draenei RPer to know.

The draenei, which means "exiled ones", are a faction of uncorrupted eredar that originated on the race's homeworld, Argus. 25,000 years ago, under the leadership of the trio of Kil'jaeden, Archimonde and Velen, the eredar had an arcane-based society comparable to or more advanced than today's Quel'Thalas; but then Sargeras turned the first two leaders and their followers into the demonic man'ari eredar, forcing Velen and his people to flee Argus on a dimensional ship provided by the naaru K'ure. During their travels, the naaru introduced the draenei to the Light and promised that they eventually would be part of the great Army of the Light, which would put an end to the Legion. [Burning Crusade Town Hall: Draenei]

This ship was not the Exodar or Tempest Keep - after it spent thousands of years traveling between worlds and finally landed on Draenor, it became known to the native orcs as Oshu'gun (the Mountain of Spirits), that giant white rock in Nagrand. Oshu'gun is a holy place to both the draenei and the orcs, containing the weakened K'ure and the spirits of orcish ancestors. [Rise of the Horde]

The draenei spread throughout their newfound "Exiles' Refuge", Draenor, building cities, the largest of which was their new capital, Shattrath. For centuries, they lived in peace with the orcs - although the two races largely kept separate - and warred against the primitive natives of the land, first and foremost the ogres. However, eventually Kil'jaeden, with the help of the warlock Gul'dan, turned the orcs against the draenei. The newly-formed Horde, under the Legion's influence, waged genocide against the draenei, ending with the fall of Shattrath. [RotH] The once-great draenei cities were left in ruins, eighty percent [Town Hall] of the population perished, and many of the survivors were mutated by the fel energies that poisoned the very land of Draenor and turned into the krokul, the Broken, mistrusted by and mostly isolated from their uncorrupted brethren. One of these Broken, Nobundo, would then go on to found draenei shamanism. [Unbroken]

Most of the survivors flocked to Zangarmarsh [RotH], where they hid until a new contingent of naaru, drawn to Outland as a strategic location for both the Legion and the anti-Legion forces, arrived in another dimensional fortress, Tempest Keep. With the naaru dispersing throughout Outland, Kael'thas Sunstrider and his blood elves seized control of Tempest Keep. In response, Velen's draenei launched an attack on the fortress and departed Outland in one of its wings, the Exodar. However, when the blood elves sabotaged its engine, the Exodar crashed on Azeroth, or more specifically Azuremyst Isle, beginning the story told in TBC. [Starting quests on Azuremyst]


2. Age

First things first: http://wowpedia.org/Life_spans

In the Warcraft universe, longer-lived races also mature slowly. Regrettably, no definite figures exist for the draenei. They are an extremely long-lived race - possibly immortal; although there is no evidence either way about the entire race, Velen is explicitly called immortal in the new starting narration. Whether mortal or immortal, they live at least long enough for some NPCs, most notably Velen but not limited to him, to remember Argus, which makes them more than 25,000 years old. The closest we have to the rate of maturing is a reference is Rise of the Horde, where Durotan notes that a child in Telmor remained virtually unchanged for about three decades.

I've used the night elf figures as a rough reference for Sikon, so she's an approximately 300-year-old equivalent of a human twentysomething-year-old. I can see strict lore-adherers trying to avoid exact numbers. It's safe to say, however, that today's adult draenei were born long before the rise of the Horde. Your character could be born on Argus, on one of the worlds the draenei visited during their flight from the Legion, or on Draenor in times of peace - but in any event, they remember the orcs turning evil and destroying their civilization, and everything that followed then.

This wow.com article: http://www.wow.com/2008/06/01/ask-a-lore-nerd-youre-how-old/ - contains some speculation (not canon) on what exactly it means to reach adulthood at a later age for long-lived races like the night elves and draenei.