The Art of Skimming in D&D

In real life, nobody likes a thief.  But in RPGs, players often play as thieves of some sort, either through action or character class.  Violent thieves, at that.

Dungeon Masters Guide, 1979

Even if you've never played alongside a sticky-fingered thief of a PC (thieving players are a different discussion), you've likely heard or read the stories.  The greedy thief scouts ahead, finds some sweet loot, pockets it, and keeps it all for themselves.  The other players get upset, and the game may end for one or all.

"It's what my character would do!" is often the thief player's defense, because many times, the other players are well aware of what has gone on, even if their PCs are oblivious.  The trouble with this defense, aside from it being code for "I want to be a dick," is that in a game based on fictional violence, where the PCs are violent people solving problems through violence, "it's what my character would do" is exactly why killing the troublesome thief would happen, likely sooner than later.

In games where XP comes from GP, this is moves from being a venial sin to a cardinal sin, as no player enjoys having their XP stolen from their PCs.  

Still, thieves are a necessary evil when there are traps to be disarmed and locks to be picked, and arguably moreso when the black market and sketchy shopkeepers are needed to buy or fence items of questionable provenance.  So players continue to play thieves (or rogues, if you prefer).

We know that thieves will be thieves, and treasure won't steal itself, so if this is how you're gonna play your thief, keep the skimming to just that: skimming.  

1. Don't claim all the hidden treasure, just a bit of it.  Players will let this slide because they are still getting part of it.  If nothing else, this will allay suspicion.

2. Don't claim the magic items, especially the ones you cannot use - odds are good the DM put it there for a reason and your selfishness getting the other PCs killed, while in character, can result in hard feelings.

3. Don't always skim, especially if being watched.  Disarm the trap, pick the lock, and back away.  Any time you're rolling the dice (like some form of skill or ability contest against other PCs) you risk losing and getting caught.