It's been a while since I've tried doing double exposures in-camera on an engagement session, but yesterday we had a great opportunity with spring around the corner and just enough time to spare during the golden hour. Double exposures basically  expose two frames and then over lays each other in camera. You can also do that in Photoshop, but newer cameras are capable of that on their own. In this example I exposed for a silhouette then with a second frame filled it with those pink flowers, with live view mode enabled, you can even see what's happening live, pretty cool and way more fun than photoshop.