Using nulls as the control mechanism for your camera or object paths is a simple and yet often overlooked technique. Think of a null object as a camera rig. You can attach everything you need to it and move it all at once...and the movement is a lot smoother and more flexible.
Here I demonstrate a simple expression to tie the emitter position of a particle light-streak to a null motion path, which makes animating my particle path over some aerial mountain footage a lot easier!
The mountain footage comes from the VideoBlocks stock collection at:
With the free 7 day trial, you can download this footage (and more!) and work along with this tutorial if you are unfamiliar with using nulls, writing expressions, or creating particle streaks.