I am a masters student at a top-rated US university in electrical engineering. I have been working under a professor who joined the department last semester. He is quite happy with my progress, but can't offer me a PhD as he doesn't have enough money. He has agreed, though, to help me get a PhD by recommending me to other professors. However, the task of finding a professor is on me. The issue arises here, as in my department professors don't actively search for students. It works mostly like a referral system, where they take up recommended students. Thus most of the openings get filled up before they make a public announcement. One way to solve this is to write mails to several professors to ask for openings. What I am looking for is whether there is a better strategy?