I've done several  giveaways of different types now, and I've gotten a few questions about how they actually work. I realized it might be a good idea to do a mini-FAQ about my contests.

Generally, I do a handful of different types of giveaways:

Code & Clue

This is the guerilla-style, no-warning, shock-and-awe-and-free-stuff method I use most often on Twitter and Facebook. Say I have a code that you can redeem on Xbox Live or PlayStation Network or Steam. I might post that code to one of those social media services with very little warning, and leave a few key characters out. To figure out the characters, I generally put a clue up with it. If you solve the clue, you'll figure out the letters or numbers that are missing. Then it's a race -- be the first to enter the complete code at the appropriate online storefront and you win. (Here's a sample of what these look like.)
Number of Winners: One. First person to enter that code wins the content. The code only works once.
How Not to Win: Well, be the second person to enter the code.  But it's worth noting that saying "I missed that one, can you just send me one directly, I really want it" does not increase your chances -- I'm never going to just give someone something that way. I want everybody to have a fair shot at it, even if it's chaotic. OneOfSwords does not negotiate with beggars.

Facebook Comments
I don't do these often, but on Facebook,  just leave a comment (just one per person, please) under the post about the contest and you're entered. Your chances don't improve if you post something clever, but my respect for you goes up, and that's worth...nothing, I guess.
Number of Winners: Varies depending on the prize in question.
How Not to Win: If you post on the Facebook Wall instead of comment under the contest post itself, it's just gonna get deleted.

Website Giveaways
These are less time intensive and generally last for a few days, since I know some people can't check Twitter or Facebook as often as they might like (or perhaps they hate either or both), or maybe they're in a time zone where they're asleep while I'm giving stuff away with the other methods. Sometimes I will ask a trivia question and pick randomly from the correct answers, sometimes it's just a straight-up random drawing. Either way, as long as you get me what I need by the stated deadline -- and you only enter once -- you're in the running. Prizes go out via FedEx.
Number of Winners: Varies depending on the prize in question.
How Not to Win: Make sure you actually send in all the information requested -- omitting part of the answer or even your complete shipping/contact information is currently the most common way to lose. You should respect the "one entry per person" rule. If I see multiple entries from the same email address, I'm gonna nuke 'em all. And once again, save your sob stories and suck-ups in the contests: OneOfSwords does not negotiate with beggars.

Podcast Trivia

Every week on the One Of Swords Podcast, I try to answer a question sent in by a listener in the "Stick It to the Dan" segment, and the winner gets a mixed box of random stuff. This can include games, shirts, hats, toys, stickers...pretty much anything you can think of that can be used to promote a game, I'm asking folks to give to me for these giveaways. No two prize packs are ever exactly the same because I'm always getting new bits to give away. And yes, I take requests -- the form you fill out includes your personal wishlist, which I always attempt to incorporate in some way.
Number of Winners: So far it's been one per week, but you never know.
How Not to Win: Don't listen to the podcast, for one. We're always hungry for new questions in this segment, so it's worth trying to create one!


Other questions that have come up:

How do you pick winners?
I use random.org to pick numbers. If there are 250 comments on a Facebook contest or 250 e-mail entries to a giveaway, I simply go to random.org, put in a range of 1 to 250, and tell the website to randomly pick numbers within that range. Then I match the number up to the winner -- very fair, very impartial. If it's a Twitter contest, same thing but it's hard to see all 250 responses in one place, so I choose two numbers -- the first is the page of entries from Twitter's search results, and the second number is the position on that page.

Why doesn't OneOfSwords negotiate with beggars?
My reasons are explained in detail here.

Did I win?

Check the giveaway post itself after the entry deadline passed. I always post the winners on the original contest's blog entry, near the bottom. If you see your name there, you won!

Are your contests only open to United States residents?

No, but the games I have access to are always the US editions. US PS3 games reportedly run fine in UK consoles, but US PS3 DLC codes will not work correctly on the UK PlayStation Store. So while I like giving people free games, I would prefer if the winners can actually use the game as something other than a trophy.  Other physical prizes, like shirts or hats or GH faceplates, can be shipped internationally, and I'll do that until someone tells me to stop (and to be fair, they might). I will try to make the Customs issues there as easy as possible, but I do have to declare the contents or I get in trouble.

Why are all the codes you give away only good in the US/North America?

I am based in the US, and I do not have access to EU or UK store codes. If I could get them, I'd do giveaways, but I can't, so I don't.

I only see you giving away [one platform's] codes. Why don't you give away [the other platform's] codes?

You may not see it because you are only looking for your favorite platform, but I do give away codes for multiple platforms -- and I give whatever I can pretty much as soon as I get it. Please understand that I am not sitting on a big pile of codes for everything Activision has ever made. When something is a new release, I sometimes get a small collection of codes (sometimes a dozen, sometimes less) for that product within a few days of its release. So if you see me giving out 360 codes for, say, Call of Duty DLC, it's probably around the time that there is new 360 COD DLC available for sale -- my code giveaway is timed to help promote awareness of that content. Furthermore, I don't have PS3 codes because that content doesn't come out at the same time. When it does come out on PS3, I might have some PS3 codes to give away, but the 360 ones will be all gone by then. I am interested in making as many gamers happy as possible, but I am unable to create perfect parity with every giveaway.

Why do you give away PS3 and 360 codes during the day on Twitter, when I'm nowhere near my PS3 or 360?
Because you can also redeem them online, via your web browser. If you are stuck in a cubicle farm, bookmark the PlayStation 3 store account management page and the Xbox 360 "Redeem Code" page to have your winnings waiting for you when you get back to your console.

Do you collect my mailing information and phone number for nefarious purposes?

Nope. I am not keeping any of the info you send me and I'm not harvesting your personal data for a marketing database or anything like that. I only ask for the phone number because I send out the prizes via FedEx, and they require a number in case things go wrong with the delivery and they need to contact you (and this has happened). I have no interest in selling you out to spammers.

When you say entries are due by a certain hour Pacific time, what time is that where I live?
I have no idea, but the internet does. Pacific Time (which is my local time in Los Angeles CA) is GMT -0800, but it's much easier to use timeanddate.com to calculate your local time based on Pacific. Even easier: Just enter as soon as you see the contest. What are you waiting for?

Why don't you give away [this thing I want] via [this method I want]?

Because a contest is not a democracy. When you get stuff you want to give away, do so however you see fit. I'll still enter to win! 

Got more questions? Ask away and I will update this as necessary. And good luck!