Capture as much light information as you can

The sensors on smartphone cameras have limited dynamic range, or ability to capture information from the brightest part of a photo to the darkest. To ensure you’re capturing as much light information as possible, set your exposure (by tapping on your screen) to the brightest part, which is usually the sky.

Even if it produces a dark image, you can generally recover it using mobile editing software like Lightroom or Afterlight.

Source: Tech CNBC
Here's how you can take better photos with your smartphone