If you are both using goggles, sometimes it's best to have a 3rd party as a spotter.
If flying with another Mavic, try to keep 7-10 feet away from eachother to avoid stepping one eachothers frequencies (and toes).
If flying with another droner and they are using a really powerful Taranis type controller, be careful. I almost lost my poor Mavic earlier this year when I was flying with some racing drones, and one guys radio just drowned out mine and sent my Mavic flying into the bushes.
I fly a Mavic 2 and a buddy of mine flies the Phantom 4 Pro V2. The only time we've ever experienced a slight bit of interference was when we were standing 10 or 15 feet apart and accidentally had one controller pointing toward the other. So, we make an effort not to do that.
Apart from that, we just let each other know what altitude we're at and keep at least 50 feet difference.
This photo is a screenshot from a video I made of a 650' smokestack being prepped for destruction. My son and I were both flying and not paying much attention to the other's position. I was orbiting counterclockwise in point of interest mode when I caught a quick flash of something crossing my screen.
We now call out altitudes and location relative to landmarks when flying together!