How should I answer when asked why I left or am leaving my current job during an interview?

Depends on why you left or are leaving your previous job, if you are not a white, male who at least claims to be Christian you are going to have issues or not last long here either.

I should be honest on why I left my previous work

Explain honestly and with diplomacy

That u didn't see a future with that company

Looking for more of a challenge.

I am searching or am leaving for an opportunity where I and my contributions add value and are recognized in that light.

I like what I do and definitely enjoy the people I work with but I’m looking for doing something I love to do. Currently I am an 8 out of 10 ...I want my next challenge to be a 10 out of 10 for me personally.

Be as honest as possible without being overly negative. Tact is an important skill and if you're interviewing, both you and the interviewer want to make sure you're a good fit from both a skills and work culture perspective.

Honestly, without dwelling on the facts more than is necessary.

I am leaving because I have more Bill's to pay so I need a more paying job.

Don’t say anything bad about your prior employer.

Give an honest response with no spin. Stories always unravel. Tell the truth, even if it's not the prettiest.

Honestly; without being derogatory about your manager or company. If you are unhappy at your current role; identify why and then answer honestly. If the position you are interviewing for is a step up then again, answer honestly that you are looking to contribute at a higher level and your current company / role is not able to offer that opportunity.

Don’t say “better opportunity” or “get more experience” or “add to my resume. NEVER talk bad about the company your trying to leave Say “more growth potential and potential to make more money” or “your feeling stagnant because there is no more for you to learn and your ready to be challenged”

I am looking to improve my situation and advance my career

Honestly, but without disparagement of the company or of the people you worked with.

Seeking new opportunities for grow and development

Leaving in pursuit of a specific interest that your current employer will not empower you to pursue (ie. leaving a sales position to pursue a creative marketing position) shows a goal-oriented determination that is very attractive in a new hire, but be prepared to present a strong case for why your previous professional work gives you an edge over people who have more experience in this new role. I always also recommend that job searchers focus more on shared company values and mission over required skills and experience, as culture-fit will cover a multitude of sins.

That it's not a good fit for your skills, or that there is no growth, or that there are workplace problems beyond your skills to manage.

Depends on if you are honest about it or not, most lie about it

You should have a solid reason that involves self growth, earnings potential and/or life balance. Never bad mouth the company you are currently with or say how bad it is to be there.