First let's look at some of the reasons you may end up with an unsatisfied guest, and some creative ways to deal with the problems. (warning: my "not best" work to follow)
1. This business is subjective.
Let's face it, we are artists and art means different things to different people. We all have a style and it's not always going to please the client. I know, I know, they should be able to look at your website and know what it is you do. Occasionally people just like your work and don't pay attention to whether or not it's a good fit for their home, their child, or their family. Maybe you're so cool that you are a status symbol and they want to be able to say that you took their picture. And then, when it's all said and done, they don't like the finished product.
First of all, there are reasons to have a solid contract and this is one of them. If you spend the time you should get paid. If the client hates the images they will not order product, but you should not back down on getting paid for your time. Offer to re-shoot the images if you can come to a clear understanding of what they really want. If that is simply not going to happen, have a few friends in the business that you can refer them to. This is something that works for everyone's benefit. You can help each other out of sticky situations.
3. Cold feet
Well, I hate this one but it happens. I have had clients come in for a consultation, book a session, spend 4 hours in my studio with their newborn baby, and never come back to see the pictures. This isn't exactly an unhappy client, but a client that doesn't want to spend the money. See, the session fee was paid so they come to the session. But the sales session is where the real money gets spent. There are a couple of ways to handle this situation. First of all you can just continue to wonder what happened and why they never showed up. This is the wrong way to handle this situation by the way. The second, and correct, way to handle this situation is to pick up the phone and call them. Maybe they hit a bump in their financial road. Maybe you offer a payment plan. Maybe they just changed their mind about how important the photos are to them. It's disappointing when this happens but I don't take it personally. I have had this happen just a couple of times. I chose to provide the new moms with one digital image from the session. A freebie. One client was very grateful and I have seen her in my studio a couple of times since then. She also eventually purchased some of the newborn images. The other client I have still never heard from.
The bottom line is this: We all know the customer is NOT always right. And some people are just cranky and hard to please. Honestly, there are people out there that just like to make trouble. Is it fair? Of course not. But we are business owners and that is HARD, not FAIR. Choosing to treat our clients with kindness and respect, especially when they are being difficult, is what sets us apart from other businesses. Earning a reputation as fair and honest, and as a business that stands behind its work 110%, will bring in more of the kind of clients we really want to work with.