Your contracts should clearly define the project deliverables as well as the process, method, and timing for presenting and refining those deliverables. Many of these details will be defined by the specifics of the project context and your own preference or standards, but there are a few general practices you should observe in order to maintain the professionalism your clients expect and deserve.
Design quality is found neither in a collection of guesses nor in a scattershot presentation method. Your design process may involve many trials; may result in dozens or hundreds of candidate efforts; may bring to light several good and viable options. Despite the numerous designs you may produce, likely only one or two excellent finalists will emerge from the rigors of your strongest efforts, robust culling process, and meticulous refinement. Only these should ever be shown to a client.
Present only those designs that you are certain will best serve the client's overall needs. One or two options only. Ever. Anything more will embody dalliance and lack refinement, and will betray your inability to arrive at an elegant and wholly-functional design. Never push onto a client a decision you should have made before showing them something.
Don't merely show the designs to the client and leave them to fend for themselves (unless the “design” need only be pretty to look at). The design is the result of a host of deliberate choices that you've made. Explain those choices and the results they're meant to garner…and why those results are likely. Explain why certain elements or configurations or other things are important. You are, after all, designing experiences and/or user responses and working toward specific results. Make clear how you've fulfilled your mandate.
Before you present your design(s), detail precisely what sort of feedback you're looking for at the meeting. It is likely that you'll want to allow your client to spend some time with what you've presented before making any final decision or offering up any detailed list of thoughts or concerns. So in that case make sure that your client knows that you're only interested in their initial impression to start. After presenting, work with them to determine the upcoming deadline for their comprehensive feedback.
In your design presentation you must give your client something to evaluate beyond how pretty (or not) the design is. Demonstrate your skill, understanding, and reinforce your professionalism. This is all a part of what your client is evaluating when they evaluate your design work. Reinforce (and reward) the confidence your client has invested in you. Demonstrate the professional capacity they've been expecting.
Presentations or other milestones are not ends in and of themselves. They are springboards toward the next step in the process. Be sure that every touch point or milestone ends with you clarifying what's next, who's responsible, what result it will eventuate, and what the deadline is for that milestone. Get acknowledgement of everyone's understanding of what is to come next. Then move forward.
Eventually, the next step is project signoff and final delivery of the work. Congrats!