Stop the fans to prevent motion blur. Avoid using the flash and instead go for an LED flashlight that can be positioned at an angle.
Zoom in/out to get the focal length that looks best for the image frame you're trying to capture, but avoid zooming in too much. You cell phone camera will have an "optical" zoom amount from it's widest setting to probably around 35-50mm, then it will start using "digital" zoom which means it's cropping your image, which means diminished quality. On my iphone 1-1.6x is optical, everything afterwards is digital.