From: Phoenyx

Your basic carrot and stick. For the GM that wants to cut down on the combat and encourage role-playing activity, you make the latter rewarding and the former detrimental.

Characters that dive in to the Thieves' lair and fight everything in sight find the McGuffin has been killed, and they can't get the vital information to stop the plot against the Duke. They later find out that had they talked their way in, they could have gotten the information, and up to the point they attacked, the thieves' guild did not know them as foes.

Just one example. In modern games, use the law as a deterrent to fighting. They get done trashing the local "Cobra" base and find that the "Front" has called the cops. They have a SWAT team waiting for them and a lot of questions to answer. Their "special clearance" might get them off the hook, but the time lost was critical. By talking to the local police, they could have isolated the base, rendered it useless, and gotten on with their plans, all with no additional effort to themselves. However shooting up a block will get them "Spanked".