For a friend (honestly, not me!) who has wilful spirited children 
DF is frustrated by their behaviour but will tell them 12 times not to do something before following through with some strange unrelated consequence which takes the DC by surprise because, after 12 warnings they aren't expecting any consequence at all so they have a massive tantrum (understandably). DF doesn't want to upset the DC by being firm or bossy 
Is there a nice book that explains all this - about logical consequences and warnings and expectations? Or lovely parenting books that might help and make DF feel better.