Are we supposed to mark giveaways not received before contacting the creator?

you definitely ARE supposed to mark it not received before a week has passed

You can't mark it as received/not received until one week has pased.
The creator has to contact the winner during that week
EDIT: You can't mark it as received/ not received until one week has pased.

Please be patient and do not contact them during this time.

This is there as a means of stopping peeps from contacting the creator as soon as the gib ends and demanding their free game. Even though you are given the option to mark not received after the week has passed, you can opt to not click on it (thus ignoring the win for the time being) and contact the creator first to see if there is an issue (maybe he needs more time, etc.).

the instructions need to be amended Winners should correctly mark their gift as received or not received within one week of the giveaway closing. should read Winners should correctly mark their gift as received within one week of the giveaway closing, or not received no sooner than one week of the giveaway closing

You should wait a week, mark as not received, and then contact them. Some people get upset if you contact them early, because they have other things to worry about, and while most people are prompt, patience is not terrible. Basically, wait a week, then contact and mark as not received. Perhaps give them a day to respond before marking not received, but you're within your right to do it if they don't send the gift in a week. If people are upset that you contacted them after they didn't send the gift, or that you didn't contact them earlier, it's their fault for not doing their part of the system.
Or, to say it simply:
One week passes > mark as not received.
One week passes > contact creator.
Less than one week has passed > do nothing..

people voting for 'second one' and 'both'... *facepalm*

I don't understand, your question seems to be serious, yet you apologize for forgetting to add "potato" to the poll...

Wait a week, try to contact them, then mark it "not received" if they don't deliver the gift.

I don't really get why anyone would get mad that their GA was marked as not received before being contacted. THAT is what seems backwards to me. If you didn't contact the winner the entire week to tell them that you have some kind of an issue which is delaying the delivery of the game then of COURSE they're going to mark as not received. Especially with the whole taboo around asking the GA creator to deliver the game. If you are not communicative then why do you expect the other person to be? (using "you" as a general term, not you OP).

The way I see it, it's up to you. The "mark as not received" option is literally "mark as not received after 7 days". If that is what happened, then that's what you can mark it as. You can choose to then talk to the GA creator from that point if you so wish and if they DO deliver the game then you can change it at any time.

Alternatively, you can choose to leave it as "awaiting feedback" after those 7 days if you so wish and talk to the creator. Either way, it ends up being the same thing. You're going to either mark it as received or not received after you've been either granted or denied the game.

How could i contact the gifter ? Where can i find hes email adress on SG ?

I tend to send the Steam key about 1-2 days after my GA ends.

However, I'd really appreciate the winner to contact me first if they got an invalid Steam key before marking it "Not Received" silently after a week.