The usual rule of thumb is that you can handhold a shot not much slower than your lens focal length, but there's so many variables that I doubt this helps very much. I have a pretty good technique (try to lean against a wall or a tree and breathe slowly and evenly). These were handheld yesterday at 1/15 and 1/30 using a Canon FT-B w/ a FL 135 3.5 lens loaded w/ 200 ISO film. Usually at 1/60 to 1/125 I can nail it that focal length, but the light was really bad. Not all of the shots came out this good, but then again nothing was posed. I just started shooting while people were working in the pottery studio, and boy, people sure move around a lot in there.
The lab developed and printed the roll using no corrections because I wasn't sure if this camera exposed properly, or if the phone's light meter app was accurate. Fortunately, the exposures were quite accurate, and the lens turned out to be great for portraits.
My apologies for the lousy colour and scans. This was crappy Walmart Fuji film, and I had to scan the lab's 4X6 prints on my low end 3 in 1 copier/scanner at home. One pic was desaturated into B&W, but Tri-X it ain't :]