How the heck did I get an alpha invite?
There are only two ways you'll get an alpha invite. Either you know someone from Blizzard, or you know someone who knows someone from Blizzard. No public keys are given out for the F&F Alpha.
How the heck did I get a beta invite?
Either the above, or you opted in to the beta lottery on your Account Management page or won it via a giveaway.
What is being in the alpha/beta like?
The alpha is a fairly small community, with a dedicated forum hidden to any player not in the testing phase. You'll have direct contact with the developers via the forums. In return for being given access to the expansion so early, you're expected to pull your weight by reporting bugs and testing all facets of the available content.
You should have no issues finding groups or questing partners. The alpha population tends to be very knowledgeable and friendly due to their Blizzard connections. And beyond that, there's a zero-tolerance policy for asshattery -- you might even have the privilege of being banned by Tom Chilton!
What's usually available when the Alpha starts?
In the case of Cataclysm it's likely to be the starting zones for the two new races and an assortment of finished Azeroth zones. This will be expanded over the course of the testing period until almost all content is available, at Blizzard's discretion.
How often is new content added?
All the time. Patches are quick and content is added in chunks. Talents, spells, quests, and other content is changed sometimes in direct reaction to player feedback on the forums.
What's the uptime like?
Equivalent to PTR uptime. Days of activity followed by a quick patch, usually.
Who can I talk about the alpha/beta with?
If you're in the alpha, then you can talk to other people in the alpha about it. Don't talk about it in the live game or publicly online. Entering into the alpha puts you under an NDA which has legal ramifications if broken.
If you're in the beta, everybody!
Do I have to start over on the alpha/beta, or do I get to copy characters?
Generally, you have the option of starting a character at level one and/or copying one or more of your live characters over onto the alpha/beta server. You do have a limited number of copies per testing period -- usually a few for the alpha and then a few more for the beta.
What can I do to prepare my character for the alpha/beta?
The first thing you should do before copying your main is to load him or her up with a ton of gold. Ask some friends to borrow all the gold they have for half an hour while your copy goes through, ensuring that you have all the capital you need to pay for whatever gold sink Blizzard has in store. And training, of course.
And don't forget that you can transfer the same character more than once to multiply your fortune.
What if I'm mostly planning to level a goblin, worgen, or new race/class combination?
First, do the above, to make sure that your new character is well-financed. Then, make sure that you have the appropriate heirlooms for your desired class. If you don't have the badges to permanently spare, just buy the heirlooms right before your copy starts, and then sell them back to the vendor once the copy finishes. Remember, heirlooms will work for your worgen or goblin!
Also think about potions, mats for leveling professions, and BOE gear for each particular level jump.
So what should I do once I get into the game?
Play it! Remember that your responsibility as a tester is to test, so play anything and everything in the expansion to make sure that the final product is picture-perfect when released.
Make sure that you provide lots of feedback on the forums. The developers hang out on the beta forums all the time and are very, very likely to read what you write, and even act on it if appropriate.
Above all, just make sure that your alpha/beta key isn't being wasted, because there are people who would waste you just to play Cataclysm early.
World of Warcraft: Cataclysm will destroy Azeroth as we know it. Nothing will be the same. In WoW.com's Guide to Cataclysm you can find out everything you need to know about WoW's third expansion. From Goblins and Worgens to Mastery and Guild changes, it's all there for your cataclysmic enjoyment.