I disagree with most of the foregoing.
Do not attempt to look into a crystal ball and predict which customers will be “good” and which ones not so great, and then decide whether or not to do business based on that presumption. You’ll quickly find yourself shunning more business than you take on. That would be fine if your first work was on par with, say, The Catcher in the Rye, and would pay you royalties for the rest of your life as that book did for J.D. Salinger while he decided to live like a hermit after writing it.
What you need to do a better job of instead is being very clear to prospective customers who don’t know you, and especially those who give you the “difficult-to-please” vibe that these ones did, exactly what they can expect: One photographer; one camera; x hours; approximately y number of photos, etc. If you can, specify down to the number of prints, size and finish, paper that they’re printed on, etc. Be as explicit and detailed as possible.
Make the contract as detailed as possible so that you know exactly what you’re committing to in terms of time, quality, the pains you plan to take over and above your normal assumed high quality and care, OR so that they know in advance the corners that will have to be cut to meet their specified price, and will have no basis for later complaint on that basis. Be clear on what you expect to deliver, and then deliver at least that and hopefully a bit better than that.
Don’t turn away business, and don’t cut your prices just to get a foot in a door – which you may not want to enter in any case. If you want to be in this line of work you need to be highly professional; sometimes that might mean going with your gut to charge twice what you might otherwise to a more laid-back and mellow couple, but it does not mean “No, I don’t want this work because it might be too much trouble.” Being in business means – same as with cops, firefighters and Marines (to name a few) – looking for trouble and walking into it with your eyes open. (Yeah, hopefully this won’t be that much trouble…)
Take the work if you can get it, and price accordingly.
A psychological aspect of this that you also need to learn in your bones is the one that states “that which we achieve too cheaply we esteem too lightly”. Meaning, if you cut your price too low they’ll think that you’re no good at all and they will have more reason to find fault just on that basis, and not less. Don’t try to approach this work or any other as “the cheap alternative”, or it’s how you will be regarded. Don’t build that reputation for yourself.