'Great Design' takes time...
Please be upfront about your expectations, and negotiate timelines in advance. Many designers can be frustrated by last-minute requests for changes or unreasonable deadlines which force them to cut corners. To get the best work from your designer, be sure we have the time we need to do it.
If you're in a hurry, you can help expedite the process by supplying all the information you can upfront and making sure you are quick to answer any queries or give feedback on new drafts. Every hour spent waiting for feedback could be another hour polishing your work.