Some of my clients expect two (or more) concepts from me. But that's a lot of work, and I would prefer to show just the best one.
Good design is not found by picking from a pack of arbitrary options, but is rather the result of deliberate choice of direction. Taking a random approach to design is never effective. Our responsibility is to ensure that our clients don't shoot themselves in the foot.
The only person who knows how many design options are appropriate is the designer who is engaged in the process. And in almost every case there is one best design solution. Sometimes another compelling direction is worth considering and presenting to the client, but this cannot be known until you have fully engaged in the process, conscious of the parameters specific to that project.
In most cases, we'll explore a host of options during the design process. A thorough exploration will weed out a number of options, leaving only the most appropriate and compelling candidate(s)—one or two. These and only these design options should be shown to the client.
As a design professional, our responsibility is to define how many design options to present in a given situation. If a potential client insists on a less effective and less professional process, we need to explain why that does not serve his best interests. Compromise never brings excellence and weakens design and therefore effectiveness.
Our clients deserve and are paying for more than a compromised design.
(Article gleaned and adapted from Andy Rutledge's in Smashing magazine)