In the case of freelancers who own substantially prominent freelancing businesses, choosing the right clients can also become a chore. Which among these clients looking for your services should you choose? Yes, this is a problem that some other freelancers would like to have, but it still is a problem, nevertheless.
First of all, you should be able to assess the interest level of your potential client in the service. Is the potential client serious on hiring your service, or is he/she merely looking around for potential freelancers as well? If time is really that important to you (and I am sure it is), then it is obvious advisable to go with the former.
It is also important to ask first when the potential client wants the job to be completed and what his/her budget for the work is. You know your own time, and I guess you alredy know how much your work is worth. If the time-budget ratio is good enough for you and you think you can put it inside your schedule, then there's no reason to worry about the job.
Finally, a serious client is a client willing to discuss the specifics of the project. He/she is willing to divulge contact information, which is important in any business agreement. If the potential client remains reluctant discuss details of the project or his/her contact information, then you may be just wasting your time. Just move on to the next client, since it is assumed beforehand that you have too many clients waiting for your response.
Again, not all freelancers have this problem and, in fact, may not have it at all. Consider yourself lucky if you find yourself too busy to have another client. Once you do finalize an agreement with a potential client, give importance to it, dedicate yourself, and see yourself rewarded.