What's the most efficient way to know what's on the market?
The primary source of information abut what's happening today in the housing market in the local Multiple Listing Service. Brokers throughout your area enter properties for sale into the MLS, and an agent can show you any home listed, or in some areas the agent calls the listing agent first.
Before you actually hit the road you can search the system to find homes that meet your description: area, property size, kind of home, style, number and size of rooms, appliances, water and heating/cooling systems; plus extra features such as fireplaces, saunas, landscaping, pools, etc.
Financial information is also included: price, mortgage balance, monthly payments, cash needed to assume the seller's mortgage (if it's assumable), whether or not the seller offers second-mortgaging, and annual taxes.