AR is a hot topic and Google has a post where they share their observations on best practices.

“From our own explorations, we’ve learned a few things about design patterns that may be useful for creators as they consider mobile AR platforms. For this post, we revisited our learnings from designing for head-mounted displays, mobile virtual reality experiences, and depth-sensing augmented reality applications. First-party apps such as Google Earth VR and Tilt Brush allow users to explore and create with two positionally-tracked controllers. Daydream helped us understand the opportunities and constraints for designing immersive experiences for mobile. Mobile AR introduces a new set of interaction challenges. Our explorations show how we’ve attempted to adapt emerging patterns to address different physical environments and the need to hold the phone throughout an entire application session.”

It’s a good summary of issues that are kind of obvious when you start down the path of building solutions.