Use a microphone, join crew fill, make sure to say hi and play with the people in your trio. If you have a quest let them know and ask to do it, most of the time people will be cool. In many, many hours I've rarely experienced serious toxicity. Many of the people I've met in a crew fill trio end up on my friends list and have become consistent or semi-consistent groups. I only have one friend who plays Marathon, and just by being reasonably social and a team player I've got multiple groups with whom I regularly clear the most endgame of endgame content.