Work this out beforehand to avoid any future misunderstandings. Then evaluate its effectiveness constantly, so everyone gets what they need. A busy day or a last-minute crisis can throw things off. Trust your gut - if you call your client at the appointed time, and it sounds like they're rushed or having a truly lousy day, ask if they want to reschedule. They'll appreciate your sensitivity.
Nothing wastes a person's time and saps their energy more than a long, unfocused meeting.
Have an agenda and a list of issues ready to discuss. It doesn't have to be formal - a list of questions or items you need to update can suffice. Send a copy of the agenda, along with any other material that needs to be reviewed, to your client at least a day or two before the meeting. Always take good meeting notes. If you can't, consider taping meetings and conference calls.