What is the best way you to get recurring clients on a regular basis?

We run a small web development agency. We have months when we are overwhelmed by the no of potential conversations going on but then suddenly there are weeks/months when we are not able to close any new clients.

So its been on and off and its hard to plan our hiring. Sometime we are short of people/team members and sometime we are struggling for new clients.

Just wanted to understand as how you guys are handling it.