A couple of things to bear in mind. If it is purely lawn grass without pernicious weeds like dandelions, dock, couch grass etc then you can do a lot with it. If those weeds are present then Round up before lifting. If you decide not to go down that route then you will have to remove the turf and stack it somewhere, grass to grass, soil to soil and cover with plastic or carpet or whatever and leave for a few years to become nice top soil. Don't believe the 'takes ayear to rot down brigade' some of ours is now 5 years old and only just becoming usable!
Next point, removing the turf means you are removing the most fertile part of the soil so you will have (ought?) to replace that fertility with something, manure, compost whatever.
If the grass was weedy you will have to carefully remove as much root as you possibly can of any weeds left in the soil.
If you weedkiller the when the 'grass' is completely dead you may dig it in to the soil or remove as you will.
If the turf is purely grass then as Tim says either dig it in broken up or remove and stack for the future.
Have fun!