Clarity and follow-through have definitely made parenting a lot easier, especially when the kids are young and testing boundaries. Using the same script each time is certainly useful, though I've had to adapt it slightly as my kids grew older and became more inquisitive. You never really appreciate how clever kids can be until they start questioning your every word!
It's great to have a united front with my partner too - we share similar values which makes it easier to stick to our guns, so to speak. But I agree with Travelmum; as enjoyable as it is to indulge the kids sometimes, there's nothing like a good, long reasoning session (tailored for their ages, of course) to really drive the message home!