First, make a connection with a little piggie. I can't tell you what it feels like because it just kind of happens. Then, make sure it's running around, it's clean, it's butt isn't wet (that's wet tail) and seems healthy otherwise and it isn't limping. Also, try to see it yawn to see if it's teeth are healthy. If it passes all of this, then see if someone can pick it up. If they drop it, pick out another one unless you really want that one and no other ones look good. If they don't drop it, ask if you can hold it and if it's nice, take it home.