@D'Ann Davis - Welcome to BP and self storage. From your description it appears you are looking for both Class C and possibly Class B self storage. I would offer there is not any one best practice for acquiring self storage. We utilize a wide variety of methods:
We acquire commercial buildings and convert them into self storage.
We also acquire land and build new.
We utilize brokers for existing facilities.
We utilize wholesalers for existing facilities.
We have our own mailing list.
Our branding is self storage so people also send us deals.
I would suggest the first step is to define what markets, and value you are looking to acquire. Another technique is driving for self storage. Driving an area, and identifying every self storage facility in that market and calling them when you are there. We have associates who have built a good size portfolio implementing this technique.
Hope and trust this assists you in our journey.