These are good tips. I'd add that unless the plumbing has been thoughtfully installed with future draining in mind (unusual in many places), after gravity drain

These are good tips. I'd add that unless the plumbing has been thoughtfully installed with future draining in mind (unusual in many places), after gravity draining it may be necessary to force remaining water out of the pipes using compressed air, especially if they are copper (PVC and especially PEX are more resilient to freezing).