By trading normally, but requiring the other party to send first and then not sending your portion. However, it is generally not advisable because you will almost definitely get caught, and the trading community keeps records of all scammers so nobody will trust you again. That can ruin your chances in making credits (and in joining factions) in the future, which far outweighs the minor immediate gain from a small successful scam at the beginning.
If it is something you really want to pursue in the interest of roleplaying, it is best to start as an honest trader and learn a bit more about how trading works before trying to scam others.
Year 9 Day 224 22:33
Deleted by Phryss. Reason: Be useful or be elsewhere.