This answer can be well explained by yourself only. Once you sit and create a chart or an algorithm of what you do, what kind of people you wish to make clients, you will find a way. That will be the best answer.
To answer nevertheless, we generate quality leads through questionnaire on the website to send us an inquiry. If the client is looking for serious business, he will spend 2 minutes to give details about the inquiry which filters any other inquiry coming through randomly from the website.
Custom emailing & detailed client profiling is another super helpful method which has given us access to quality clients & leads.