Rogues have an advantage in this as they can "peek" into another character's inventory and identify desirable items to appropriate.
Syntax: steal <item> <target>
In Game Description
Syntax: steal <item> <person> Thief skill: Steal attempts to obtain an item or money from someone without their knowing it. Your chances of success are greatly improved if you are sneaking, hiding, and vastly improved if your target is asleep. Your chances of successfully stealing an item depend upon your skill and its related skills. Be aware that heavier or bulkier items are much harder to acquire. Most people are known to take offense at being stolen from, and will likely attack you if you fail. Example: > steal gold Mournblade > steal diamond Rand