Zillow, Trulia, or Realtor.. no one responds!

I'm in the market looking for a house to rent out. My family has grown and this 2 bedroom apartment is not cutting it anymore. I reach out to places like zillow etc, but no one ever responds. And days later the place im interested in gets rented out FAST! WHAT AM I DOING WRONG? WHAT ARE PEOPLE DOING TO GET THESE PROPERTIES SO FAST? I've been looking for 2months now and I only have 30 days left to find a place. Any alternatives that worked for you? Can someone please help me out.