This achievement requires a single person to return 30 crates by themselves. You don't need a team for this but the more players you have the easier it will be. You will need to work together and communicate for this achievement. A solid method for this is playing on "Mechanized Invasion" and be sure each person understands their role. This strategy is also viable for earning "Hanging 20".
From the beginning all 3-4 players need to rush to the Church building, it's on the other side of the map from where the team originally spawns; from there each player needs to understand their role:
Player #1 - Crate Runner
This player will spend all of the preparation phases and most of the fog phases running crates to the base until they have the achievement. Once there they'll fall in with players 3 and 4.
If they go into last stand they will need to shuffle their way back to the safe zone where they can be picked up.
Player #2 - Powered Armor Pilot
This player is the team's eyes and teeth. On top of having the best firepower and defense, the PA's scanner highlights enemies and makes their location visible through the fog. On top of seeing enemies, special enemies (EPA's, ATC Phase Units, ATC Rocketeers) have a red outline. Be a team player and call out what is attacking.
This player should be very cautious of Alma. Her daze and blindness doesn't affect you that much but she can do much worse. She can remove you from the PA, teleport you to a random area of the map and have you outside the PA or simply destroy the PA.
If you lose the PA under any circumstances, your priority one is to find it. If it gets destroyed it will spawn at a random location in the preparation phase after the current fog phase.
Player #3 & 4 Base Defenders
These players should not go far from the church and shouldn't even leave the building. They should barricade all possible gaps every preparation phase and be ready to revive anyone put into Last Stand. These are the players that can make or break a game if things go sour; stay safe, stay alive.
A very important thing to remember when playing Contractions is... there is no bleedout timer. You can shuffle around the map for the entire fog phase and not die.
Find a team using the BOOSTING/PARTNER thread.