The most significant differences to stills photography are Sound, Movement and Editing
Audio is half of video and it’s probably the single hardest thing to get your head around as a photographer new to shooting DSLR video. You have to spend as much time as possible getting to know audio. In fact a great tip is to just go out with a digital recorder and ‘only’ record audio, just so you can isolate sound and learn to ‘listen’ for the sound that most appropriately enhances your story. So much of good sound recording is making sure you don’t accidentally record too much of the wrong types of sound.
When photographers first start shooting video, they tend to forget a lot of the things they already know about photography. Don’t ignore the rules of composition. They apply slightly differently, especially when your moving, but rule of thirds and everything else still apply. Plus you don’t move the camera unless there’s a reason. You see a lot of deliberate movement in video because the shooter ‘thinks movement = movies’ but often the camera has no real significance or motivation and does not move the story on.
Now you are used to editing your images, but in video you are looking for coherent sequences, a combination of shot types, angles, sizes, perspective and continuity of action. This is something that you will learn by doing. The more you edit your own video , the better your shooting will become. You must try not to be put off by the mistakes you will almost certainly make. It’s going to feel like you’re going backwards before you really hit that Ah-Ha moment. But all of this really reinvigorates you and will definitely re-inspire your passion for image making.