Buy games now if I can play them now or wait a sale.
They must scream they are for me, whenever in their presentation and/or their story and their gameplay.

If they interest me the least bit, I usually look around if I missed other games like them or old games I've bought to make some kind of comparison, it helps me decide.

And sometimes, I take a risk and try something new. I've never bought a game that I truly deeply regretted so I kinda trust me after all this time :P

Rules? Pretty simple: Get it if you want it.

No Steam
No Origin
No Uplay
No DLC
No Season Pass
No Shovelware

Any of the above goes into the ignore folder. Anything else will get a second look.

That's the reason i stopped buying physical versions; as much as i love them, nearly all of them require either Steam (or another client) or have another DRM scheme (which i don't like, unless it is just a simple CD check).

Yeah, that was both a scary and scarring experience, for me... Back in the day, one decade + earlier than now, i used to buy retail games without even knowing about steam... Or looking at their backside requirements! Hell, some of them didn't even write "Steam required to play"! Imagine the horror when arriving home, inserting that CD in the player, only to find out i had to make a steam profile and finish downloading there... As well as be on to play... Brrr, the horror, i still have NIGHTMARES from it! And a bonus hazard; i couldn't even refund it, because the code was used! *shivers*

To buy a game it should be:
1. DRM-free (absolutely strict rule)
2. one that I'd like to play soon (implied, but anyway)
3. at an affordable price (of course)
4. available for Linux (native version) or at least run using Wine
5. a complete version, if DLCs or expansions exist already

AND it should not be:
1. a preorder
2. in development (any stage)
3. developed or published by a disrespectful entity (blacklisted based on my criteria)

Not strict rules, but play a role for a purchase:
1. support a great, respectful developer/publisher
2. German language available (specially if it's the original language)
3. Flat price (not long ago, it was a strict rule)

a) without reviews there is no buy, and I mean not fanboy reviews on the site
b) a new released game? WAIT....and than wait some more time, because than maybe some bugs are fixed
and the price is reduced
c) full price? only for boxed ce games
d) for bundles..at last 2 interesting games
c) sales are nice (except something like insomania) but set a limit. There is always another chance to get games.

Unfortunately, I don't really have any, but I always research every game and watch a youtube video of gameplay. Look at reviews to see what users bitch about. One of the biggest things that prevent me from buying is an abandoned game if it has any issues. For instance, during the bundle thingy sale, I did not buy the bundle with metrocide in it because it's a buggy pile and abandoned. In order for the price to work out, I needed that in the bundle because I owned the other games.

1 - Wait for the Ultimate Edition to be released.
2 - Allow prices to drop sharply and to be on sale.
3 - Don't buy the censored version.
4 - Watch a video review before adding to the shopping cart.

(1) There are times when they take some good things out of a game and replace it with cruft on an "ultimate" release. (see "(3)" below);
(2) I support the developers. I'd rather they get a decent cut of the sale instead of the producers, distributors, i.e. nobody that had the vision to make it in the first place;
(3) I would *definitely* buy it if it were censored, controversial, or in any way irritates the sensibilities of others;
(4) I'd rather watch a few preview clips than someone's opinionated piece on the subject, I'd rather form my own opinion than have it swayed. Nine time out of ten, low-rated media has been my favorite.

2 - Buying things at full price is a luxury for me.
3 - Edited my post to be more accurate: I only buy uncensored games.

I can absolutely relate: Once upon a time, one lovely morning I bought Orange Box (mainly for Half-Life 2 and Portal). I was very excited to play HL2 (big fan of HL) that I couldn't see the time to get back home and install it. Well, the rest is what you described... And I couldn't return it for a refund since I opened the box. Thankfully, I was able to play the game (although without the expansions) thanks to a friend - don't ask for details! :P

Fast forward in 2013, one and a half year after Skyrim's release and I said "what the hell, I want to play it" (also fan of TES) so by the way, I finally installed Orange Box too and replayed HL2 plus it's expansions. One thing lead to another and I ended up with buying another 5 games that I really wanted to play (at least all of them had bargain bin prices!). Then one day I decided to never buy a game with online DRM again, physical or digital. I'm more than happy for that decision! ;)

Rule 1. No guns. Unless it's guns and swords. Or really cool space-guns. And swords and magic is stronger than guns.
Rule 2. Optional or nonexistent microtransactions, or no buy.
Rule 3. No on-disc dlc, pre-announced dlc, partial story-dlc, etc.
Rule 4. No "open world" with endless repetition and grind.
Rule 5. No repurposed license sequel due to "market demand".
Rule 6. No preorder bs.
Rule 7. No MOBA or "free" to play.
Rule 8. No Diablo clone.
Rule 9. Will not buy titles with professional marketing campaigns and no gameplay footage.

So.. kind of broken all of those rules for practically every title I've bought in the last 10 years. :p

- DRM-free, but on these forum that is more or less a given
- I usually do a bit of a reserach on games which I haven`t played yet and seem interesting, but I buy them only if I get the feeling that I'd be able to get at least 10 (or obviously more) hours of enjoyment out of them. (That doesn't necessarily mean that I have to finish them.) Of course I don't always get this right and some of the games I buy end up being way too short without real replay value or I simply cannot enjoy them as much as I thought I would.
- I don't want to come off as a cheapskate (although I probably am one) but I usually wait for sales with most games, unless the price is really low (10€ or less). The exception is when I _really_ want to play a game that I don't own yet or if I want to support developers whose previous games I really enjoyed.
- I don't do pre-order (anymore).
- I know it is rather shallow, but sometimes I am tempted to buy games just because I find the art direction/style different/innovative/simply pleasing to my eyes, but I always remind myself not to do that.
- No games with serialised content, (I mean games with season passes and such) unless all of it is already available.