How many times have you been scammed?

precisely 0. I don't really trade all that much.

What procedure should you follow before trading with someone? Please help.

Never. I'm careful with these things.

Never. I don't trade that much, and I'm careful when I do. Enhanced Steam helps, too.

Haven't been for a very long time (the last time I was scammed was in MapleStory many years ago). Nowadays, if I lose something, it's because I deliberately made that stupid decision (such as making a loss on the Steam market).

Just once. It was a somewhat big one, but it taught to be more careful in trading, and in real life. :B

N/A

0, only have a caught :)
i get a saints row IV for starbound(great offer maybe?), but this is a key then, i make the guy first send me the key, and hu? this is invalid, but after he send another working key,

then if you will trade with keys and offers are so much better you need activate the key then you will never be scammed.

Yet to happen.

Bought some bundle keys with Paypal for no profit to the seller so we're talking $0.20-$0.50 a time. Everything has worked out fine and I've probably done that about 20 times now through the Group Buys group. I know it's risky to buy with Paypal, although I figure if someone is going to rip me off for that amount of money and damage their rep then they're either stupid or desperate.

Not done too many trades of tf2 keys for gifts, only 2 that I can remember. Made sure the people were who they said they were and had extensive, provable trading history. Both guys I dealt with had over 2000 trades, loads of rep on steamdrades, hearts on tf2 outpost, trades going back 2 or 3 years, plenty of games on their account, their games weren't suspisciously cheap (they weren't even the cheapest). All the usual stuff to look out for. Nothing revoked so far.

Wouldn't pay Paypal for more expensive non-bundled games. Wouldn't pass something through the trade window for a steam key in chat.

Once. According to my account's details it was the second trade I've ever done and it's pretty funny story. The point is that I still can't call it a really bad deal.
I just discovered a world of digital distribution and had only few games (HL Platinum Pack, bought two years earlier just for CS, Orange Box traded a day before for 10 coals and Borderlands GOTY, my really first game bought on that sale. If I recall correctly I was interested in Introversion and Voxatron bundles and some guy offered me them for my six coals. I was a newbie and agreed to send my items first. Then he gave me two codes and immediately went offline. The first key turned out to be duplicate or invalid but the second activated Humble Indie Bundle 4 pack :). So I didn't get exactly what I wanted but didn't mind it at the time at all because got few new games for my almost empty account. And I still don't regret it.
Since then I made around 200 successful trades and never got scammed anymore.

Not on Steam or anything but back in this MMO named FlyFF, me and my buddy were all excited because I sold some items and got major cash and then we were gonna buy cosmetics. I bought a hard to find hair piece, and his friend who he said he knew for a long time got on and asked if he could try it on his character, and reluctantly enough I let him (like an idiot). Instantly logged off, and when he got back on and I asked for it back he tried to make me buy it off of him AFTER I already paid for it. I ended up getting a large amount of people to fuck with him and mess with him n stuff, they all pitched in and helped me to buy it back. So I guess that was my first time getting scammed

6 times, i think.

first time i lost Frozen Synapse (gift).
second time, i lost 2 copies of Portal 2.
3rd time, i lost Star Wars: Knights of the Old Republic.
4th time, i lost Mount & Blade Collection.
5th time, i lost 2 copies of Left 4 Dead 2.
6th time, i lost Terraria.

i don't think i've ever lost any keys in a scam, though

Once. Someone scammed me out of my Eaglehorn, my full set of Natalya's gear, Bartucs, a few random runes and charms too. It was very sad.

Once, but never in anything like Steam. See, when it comes to my money or property, I'm actually pretty careful about it.

The only scam I ever fell for was actually an abuse of mechanics in pay-MUD, where somebody would drop empty backpacks on the floor of a shop, and adventurers would occasionally put their stock gear in the dropped packs instead of their own. Unfortunately I lost a good arbalest that way. Oh wells~

0 but not because I was careful, followed the rules etc. With all these chargebacks, CC frauds etc. it can happen to anyone. Only way to not get scammed is not trading at all.

Never.

2 times, a Portal 2 Gift and a THQ Bundle.

Never, I don't trade

Once and it is my fail because I trust people too much,so it np but what hurts me more than that I scammed is that after I provided all proofs about scam on steamrep,they first didn't reviewed report for 5 months and during those 5 month their review policy changed so they don't review cd keys scam anymore and they market my report as invalid...

In time I posted they were research cd key scams but first they were slow and I waited 5 months,so they find time to reply that in meantime they changed policy and I can't report cd key scam anymore... GJ FKING STEAMREP

Thats what bugs me sooo much... Best I could do is to get that guy banned on reddit r/sgs and r/dota2trade but he is still not marked as scammer on steamrep,here is thread if someone for some reason wanna see http://forums.steamrep.com/threads/76561198041957904.47442/

Once, 5 keys. Learnt my lesson after that.

Too many times, Id prefer not to count

One time in Diablo 2 ten years ago. Never on steam though, 400+ transactions. Guess I'm lucky or just a smart trader. :P

0 on Steam. I've gone first countless times and never have I gotten scammed.

once, i was foolish enough to accept a non tradable tomb raider gift, it got revoked a day after trade as it was paid for by false card details