So the ticket went as follows:
Hi, in whispers I agreed upon exchanging 1700g for a variety of items with [Redacted]. Everything we were to exchange is in chat logs through whispers about ~10 minutes ago. I gave him the 1700g, and he did not furnish all the goods, scamming me out of gold. He was doing this as a scam, including 3 epics in the whispers which he did not furnish at the time of the trade, followed by putting me on ignore, which is why I decided to report this, as I'd hate to see it happen again.1) Don't be a Dick
I wasn't overall too upset about what happened, but honestly the sheer audacity that he thought he'd get away with it and that he had just ignored me ticked me off. Did I let that show in my ticket? No. Imagine a common ticket that GMs have to deal with every day. It's undoubtedly a thankless job, and I'm sure you can imagine any number of random assortments of LFR companions you've encountered that these GMs have to deal with on a daily basis. Try to remain calm, and convey your message politely.
2) Be as Clear and Concise as Possible
Now this one is really important. Hanging around the TSM IRC Channel, Consortium Forums, and /r/woweconomy you inevitably come across a person looking for help who says something like "Hey I have Jewelcrafting, how do I make gold with that?" or "TSM's not working correctly, how do I fix it?" All completely answerable questions, but jeeze I would need a heck of a lot more info. In my original ticket I made sure to include when it happened, what the questionable exchange was, what my expected outcome was, and what happened. I also made it clear that I thought it was a scam, and why I thought it was a scam, to avoid any confusion. I think specifically noting the problem as you understand it is key.
Hope this helps in the future, if you have any other tips for writing tickets, feel free to leave them in the comments below!