I use references quite often, especially with difficult poses. Most of the time I use myself, since it's the easiest way to get the exact pose I want. I have a large movable mirror that I can position anywhere in my apartment and then I just pose in front of it and snap a photo. Once I had to roll around the floor and that was a difficult one but what wouldn't I do for my comic, hehe. I've also strangled a toy in order to get a good reference for a choke hold.
Sometimes I do need references for other things as well, like perspective, lighting or scenery. I do struggle a bit with perspective, so once I actually build a small scale miniature out of paper for one scene and took photos inside of it in order to get the right angle and perspective for the scene. It actually helped a lot, so it was worth the effort!