I chose "Friends/Local Breeders" because I have a small group of breeders that I have gotten to know over the years that I look to first when I need something. I've dealt with them many times, I know they have first rate collections, I know they have excellent QT procedures, and I know they have excellent customer service.
I used to buy more at shows (I'm in Central FL, so there is a good selection of shows) and from breeders I didn't know as well as long as they have a good reputation. But, my purchases have gotten higher end and I'm just getting ultra paranoid I guess. I just prefer to stick to those I know well, and having the ongoing relationship is nice too. For example, there are a few females I held back from 2013 because I know one of the people I deal with regularly is interested in working out a trade once her eggs start hatching.
As far as where I sell the most, I advertise on Fauna and Kingsnake, and also in a few facebook groups. I also have a business facebook page and website. Facebook is the most time consuming, but I do seem to sell a lot there. I also get some repeat customers who email me looking for things. I don't vend at shows, mostly because the quarantine issue bothers me.