Building a Buyer's List

I am working on building a wholesale buyer’s list and wanted to ask what are effective ways of doing this? Thanks in adavance for your responses.

Go to your local reia club and network.
Call all the WE BUY HOUSES signs you see.
Put an ad in the paper saying that you are looking for investors and your #.
Put an ad on craigslist.
Call all the for rent signs you see in person and in the paper.

You want to find out what investors are buying, are they cash buyers, etc.