Thieving is a skill that allows players to obtain coins and items by stealing from stalls, chests or by pickpocketing NPCs.
Pickpocketing
This is the action of walking up to an NPC and right-clicking them, then selecting Pickpocket. In the case of the Master Farmer, only a single left click is required to attempt to pick his pocket. If successful, you will gain Thieving experience alongside some coins or various items. The higher the thieving level, the more NPCs the player is pickpocket from.
However, it is possible for the NPC to notice a pickpocket, in which case the NPC will yell "What do you think you're doing?" and will stun you for a few seconds and deal damage. Because of the possibility for damage, it is recommended that players bring healing familiars or foods such as cakes that can be stolen from cake stalls.
Training Method
Stalls are located at the Skilling Zone, slightly left of the teleport location. Players are highly recommended to train Thieving here as one gains double experience inside the zone.
Level 1-25: Food Stall
Steal from the Food Stall from level 1 to 25. You will gain roughly 60 coins and a sliced banana which can be sold for 5 skill tickets
Level 25-50: General Stall
Steal from the General Stall from level 25 to 50. You will gain from 130 to 150 coins and a cake tin which can be sold for 10 skill tickets
Level 50-75: Crafting Stall
Steal from the Crafting Stall from level 50 to 75. You will gain from 200 to 400 coins and a gold ring which can be sold for 15 skill tickets
Level 75-85: Magic Stall
Steal from the Magic Stall from level 75 to 85. You will gain from 600 to 900 coins and a bucket of milk which can be sold for 20 skill tickets
Level 85-99: Scimitar Stall
Steal from the Scimitar Stall from level 85 to 99. You will gain from 1500 to 1650 coins and a special cup which can be sold for 25 skill tickets
Alternative 95-99: Fat Tony
An alternative way to train Thieving from 95 to 99 is by pickpocketing Fat Tony, who is located slightly north-west [NE] of the stalls. You will gain a good amount of skilling tickets from pickpocketing him.