Welcome to Sythe! I highly suggest you take the time to read the stickies and the rules in each section before posting. Always trade safe, and take the time to research the person you are trading with. Google becomes a powerful tool with any black market.
When trading, don't ever let someone rush you into a trade you are uncomfortable with. If you ever have any second thoughts, trust your instinct. Its better to back out and save yourself before its too late than to get scammed.
Sythe has a great community, but of course with any online market, there are people out there with shady intentions. Again, always use caution and don't ever second guess your instincts. There are plenty of Free and Official MiddleMen who will be more than willing to help you with any trades you wish to conduct.
If you ever have any questions, please don't hesitate to contact myself, a mod, or a more seasoned sythe user for help.
Enjoy your stay and I hope to see you around!
^ Credits to n4n0 for the post.
Welcome to the boards/community Help, best of luck with your MW3/RS trading.
Those markets can be found here:
RS:
http://sythe.org/forumdisplay.php?f=255
Other:
http://sythe.org/forumdisplay.php?f=362