Quoting cunning cuniculi:" tried doing it with him, starting so its not such a big task, playing the pick up game (very drawn out), ... [snip!] ... drawn out), the organizer was supposed to help with this i thought.....time out once or twice....i think thats about it...."
Does he understand races? Such as "Here, let's play a game! Lets RACE to see who can put the toys away the fastest!" You will move a turtle speed but hopefully he will go quickly....
This worked a couple of times for me. Really the only thing that worked 100% of the time was taking away her doll or bear friend. She didn't want to lose either of those. Now, at 6 yrs old she still loses her favorite bear or as soon as she sees me with the garbage bag she knows that her toys will go to kids who have very little toys.
Be consistent. Follow through with whatever "threat" you place. He will learn, but remember he is only
3. It may take some time for him to get it.