As mentioned, a floated barrel helps accuracy. Basic rule I was told by a gunsmith I know is that if you can't slide a dollar bill between the barrel and the stock, you've got some more sanding to do :wink:.
In the reverse, you want as much consistent contact as possible between the action and the stock. This is what bedding does. Basically an epoxy is poured in the the action area (which is inletted out a bit before starting) and the action then pressed in, which eliminates any gaps in contact.