What methods were used during Sherman's march to the sea?

The March was a punitive raid on a state that had quit the USA in an arrogant spirit, and Grant had told Sherman to 'make Georgia howl'.

Sherman set out to wreck the Southern farms and railroads in order to starve the Confederate troops in the field.

He told his men to stick to property damage, and strictly forbade violence against civilians. When this did happen, it was not usually at the hands of Sherman's soldiers, but carried out by the lawless mounted vandals (mostly deserters from both sides) who rode alongside the army for the pickings.

Sherman's methods were harsh, and the people of Georgia have never forgiven him.

His own message to the Georgians was that their war was now lost (Lincoln had just been re-elected) and they could lay down their arms as soon as they liked. But the Confederates always wanted to show that they were not the sort of people to give up; now they were paying the price for their stubbornness.

The March to the Sea was entirely successful. It shortened the war by months, at almost nil casualties.