Every situation will be different. However, people typically try to keep a constant aperture throughout an edit. Its personal preference. I usually try to keep mine around 250. Aperture is a different story. Im always changing my aperture to allow for different types of light and different types of styles. The higher the number (f/6.3-f11) is right where you want to be for follow cams. Most things are in focus at that point, and lenses are typically shaper around f6.3-f8. If you want to shoot a shallow depth of field, you can achieve that by shooting a lower number, such as f/3.5. But remember, try to avoid shooting wide open. It is the softest point in your lens.