Make eye contact and say hello, maybe a little "let me know if you want anything". Don't stare at them.
We went to a craft fayre and as I walked past (and made eye contact to nod hello) the guy said "my wife and I do all of these in our spare time, I do the metal work, my wife does the sewing....."
And honestly, I just couldn't get away fast enough. I didn't like the stuff on display and then felt totally awkward.
I don't recall seeing any prices at some of the other stalls that I may have been interested at. Which is a huge turn off for me. I don't want to ask, to be told a figure out of my budget and then have to vocalise I can't afford it.