I always find them basking on logs where its really bright, usually in a clearing next to a stream on sunny days. We have a wildflower reserve in my town that is quite literally crawling with them.
Low tech method: I usually open a sandwich bag and put some taffy or jolly rancher in it, then place it on a log where there is observed hunting activity; these guys all tend to be in the same area hunting. Some will fly away initially, but little flies will be attracted to the bag, which is their prey. I usually come back to like at least 3 or 4 inside the bag (its much warmer in there + the food), and then I just seal it before they can exit. Works everytime, sometimes I dont even need the candy or flies, they bite down on the baggie and I just pick them off and throw em in.
Either that, or I just catch em with my hands lol