It's certainly not critical, and I realize it's kind of silly, but my sister and I are constantly losing one another in MP.
We thought it would be funny if, instead of tracking your friends on your map (very handy in a lot of games, but also unrealistic), you could instead have your character let out a cry, like "CAW-CAW CAW-CAW" and then try to follow the sound to find one another. We thought it would be hilarious and in keeping with the dynamic of the game as we see it.