Sale, almost always.

For one reason: I simply have too many games. Not as many as some, but enough for me to last me quite a while. To buy a game that I'm not salivating over at full price, leave it on my shelf for months until I see it all cheap on a sale is not a good business decision.

There are exceptions to the rule. I've bought all Starcraft games at full price and the Witcher 2 game I bought on day one and still have to play it. I just wanted to help GOG and CDProjekt and their no DRM from day one stance, but other than that, it's all sales.

Companies DO make money from sales. First day release sales help them recover their investment if the game sells well, but they make far more money with sales, which are aimed at people on the fence or are lukewarm about the game, so I see both customers as different targets. My five bucks help developers far more than my zero bucks.

Full price if it's something I want to play now, or something I know I will like. Discount if it simply "looks interesting", or if I was on the fence, or if I wanted to play it in a not-so-near future.

That depends on what full price is, and what kind of shit-ass DRM the product has been crippled with.

You have a device like that at home? I didn't even know some sites would require something like that. I've bought e.g. games online from Humble Bundle (PayPal), GOG, Steam, GMG, GamersGate etc., this is the first time I even know about such option.

Then again, I've never figured out why buying stuff online is made that easy, you just need to know certain numbers from someone's credit card (which are even written on the card itself), and keep buying stuff (until the card is cancelled).

The way I buy GOGs, here's their choice...

They get my money when I buy it on sale
OR
They get no money from me when its full price

I'm just a "buy it at the lowest price possible" kind of guy for everything.

Depends on it.
If they are simple digital copies i can wait till they are on sale.
The rare DRM free boxed games i buy after check and double checking about known issues.
These days i never buy a PC game after release cause only a few publisher test them and i don't like the
*Bananen Spiele.....reifen beim Käufer*.
Console games are better tested so i buy them at full price if they are a must have.

I finished my university master's degree half a year ago but since there's a bit of a problem with unemployment in my country and education is not all that valued here i'm still unemployed so i buy games mostly when they're on sale.

Click on the "add to cart" button then select payment method and a couple of more clicks and done :D.

On the more serious side. I read a lot of reviews (I also have played many games in my time which I didn't own and want to get), but excepting that I check and double check and triple check. Or even try a "demo" .. ahem.. anyway if the game appeals me and it has no always-online DRM or something in the line then if it is on sale (at least 75% off) then I'll buy it :)

Most Swedish sites, and many international sites require that I use that thing, a bit depending on the payment method. I guess it's mostly dependent on what bank you have, but I need to use that thing if I buy things from Gamer's Gate (which granted, is Swedish) & GMG, if I use their direct payment method option, instead of going through a 3rd party one like PayPal.
And in order to use that thing, I need both the physical card, and a number that is not written on it. It's slightly inconvenient, but I can see why they've become so common here.

Not playing the games is a major reason why I don't pay a lot. I hardly play on the PC and I don't value collection that highly that I'll spend a lot on it.

On Android the reasoning is a little different. The main problem there is that I can get a lot of games for free, but there are still games (like Shadowrun Returns) I'm willing to buy on day one and lose some money on.

Nah, just a new card this year. With the Target hack, I am expecting another new one this year. It's starting to become a frequent occurrence that I have a new CC every year.

There are games (recently: Deadly Premonition, Bloodnet) and devs (Wadjet Eye, Harvester Games) I buy at day one or pre-order if possible. I'm simply sure I'll love the game and there was no instance when I was proven wrong.
Games I don't know \ I'm not sure about - I wait for a sale.
Also: DRM = wait for sale or DRM-free version.

PC:
Full-priced - Novel, interesting game covering a theme/story or featuring types of characters I have been missing in recent games. Or it is a super-rare console port like Deadly Premonition. I like to show that there is a demand for PC games like that and want to see more of them.
Discounted - Games I am unsure I will like or I don't think they last that long (for example $50 for 5 hours long game is no-go for me). Also if it is a DRM release and I like what I see but not enough to pay full price for basically rental.
Heavily discounted - A DRM game with tons of DLCs that aren't included. A lot of Steam-only games.

Android:
I buy very, very rarely and only when it is heavily discounted. I don't view portable gaming as a long-term, complete gaming entertainment and more like a platform worth of Tetris-like time killers.

Xbox/PS3:
Full-price - 2 exclusives. One of them I bought the first month only because I knew I will be able to sell them at minimal loss. Well, later on I decided to buy it again since the game really grew on me (TLoU) however it costed me half a price including the loss.
Discounted - I use Xbox for couch-playing of my PC games, thus I buy preowned games. I have already paid publisher (and came into their money counter as a PC purchase), preowned still cost more than average PC games and they are almost never complete (ie. DRMed DLCs exist). When Xbox Marketplace sells a game for five or ten bucks, I go for it - Both such sales and me buying that are rare, though.

I Never Pay Full Price ever because over here in Australia Money Is TIGHT! I always Buy Games on sale expecialy If I can only get them through steam Fucking Steam!