I've been exploring career opportunities and have broadened my horizons from the industry I've worked in for 15 years. One of the first questions I always get is, "Why do you want to leave industry x?" What is the most effective way to answer this question? I know there have been many podcasts on interviewing which have been immensely helpful. However, I'm still having difficulty answering this question effectively.

Be candid and upfront
I took something of a sabbatical from my preferred industry for about 18 months, to reassess my career goals and decide where I wanted to go, and I've just come back to take on new challenges, and the first question I got asked by everyone was "so why did you decide to go drive trains?" (That's not a euphemism, my sabbatical was to drive trains for a living). I knew this would be a big question, and so I got my answer together early, like so:
"After completing (a really big, cool project), I found I was having trouble identifying where I wanted to go next with my career whilst being involved in the day-to-day efforts of my job. So, I decided that I needed to take a break and reassess where I was going from the outside -- clear the trees so I could see the forest, as it were. My thoughts led me to believe that where I want to go is into technical management with a leading company in the industry, hopefully moving into a larger management role as I gain skills and experience in this new area. I believe I have excellent technical skills, and would like to use those skills to help others reach their full potential, and build and grow teams of people who can excel in the field".
The key, I think, is that it is all 100% true. No dissembling, or trying to weasel around the issue. No laying blame anywhere or anything like that.
I got the idea and approach from an MT/CT podcast I listened to on getting fired, or something like that. The relevant advice was in relation to how to answer the question "so why did you leave your last job?", and the answer was, basically, to acknowledge that you got fired, and say that you learnt lots and are looking to not make the same mistakes. I'm fairly sure the podcast I'm thinking of is http://www.manager-tools.com/2011/03/getting-fired-part-1 or http://www.manager-tools.com/2011/03/getting-fired-part-2 but I'm not in a position to re-listen just now to confirm.
Obviously you're not getting fired (or I hope it's not!), but the same principles apply, I think. If you've made the decision to move, then you have reasons, and you'll get a lot more credit for being open and honest about them than trying to concoct a phony reason for it. If the reasons are really unseemly (you've been fired from every company in your industry, so now you've got to try something different), you might have to put a bit of positive spin on things, but otherwise I can't imagine why the truth shouldn't be perfectly acceptable to any company you'd actually want to work for.
If you're having troubles coming up with ways to express your reasons, it might be helpful to discuss things here. There are some really good wordsmiths on here that could probably put a positive spin on running over someone's pet -- so having been run out of town on a rail should be no problems for them (grin).
Moving toward, not away from something
I once heard some advice on this topic from a sought-after recruiter that seemed very wise to me. She suggested that when discussing your career path/aspirations, you should always position it so you're moving TOWARD, not AWAY from something.
The difference is when we talk about moving away from a scenario, some complaining or negative element tends to make its way into the conversation. When you're talking about moving toward something, it's a more positive statement as it implies you're expanding your horizons and looking to increase your knowledge or experience in a certain area.
So, rather than "I want to get away from [something you don't like] because [more negative info]" you're saying "I'm looking forward to [new, positive element]." Does that make sense?
All the best to you.
Andrea
Thanks for Sharing
Andrea, I really like that explination. Thanks for sharing. - Sam