Today I had a small chat with one of our developers, about adding a column to a table "the right way". 
I told him, that depending on how they needed to deploy it, it might be beneficial to make it idempotent. 

Heres's an example of that script: 

USE [M42Demo]; 
IF COL_LENGTH('dbo.QA', 'minnyecol') IS NULL 
  BEGIN 
    ALTER TABLE [dbo].[QA] ADD minnyecol VARCHAR(2000) NULL; 
    PRINT 'Added column ''minnyecol'' to [dbo].[QA]'; 
  END 
ELSE 
  PRINT 'Column ''minnyecol'' already exists in [dbo].[QA]';