Gears of War: E-Day

Collectibles and 100% completion:
The War Journal tracks four separate completion counters:
Collectibles: 140
Hard Cases: 125 (Act 1: 0, Act 2: 36, Act 3: 38, Act 4: 46, Act 5: 5)
Secondary Objectives: 17
Supply Cache stations: 36 (none in Act 1)
100% completion can be reached on any difficulty, so collect everything on a comfortable difficulty and play Insane separately.
Use Tac-Com to reveal nearby Hard Cases, and listen for the audio chime that marks a collectible.
Missed collectibles, Hard Cases and objectives can be picked up afterwards through Chapter Replay.
For the Quartermaster achievement, pick up each of the 17 eligible weapon and equipment types at least once, even if you drop it again right away.

Points of no return:
Sweep these chapters fully before you continue:
Hold the Line: before you link up with Charlie Squad.
The Convoy: before you drop through the bridge floor.
Technical Difficulties: before the train departs.
One Problem at a Time: before you board the final train.

Secondary objectives that can disappear:
Lost in Translation and Family Reunion depend on other objectives and disappear if you rush the main objective.
Lost in the Park and Rooftop Mayday only appear after you help Corporal Harris fend off his attackers.
Black Raven Down and Lone Wolf unlock after the Octus Tribunal Muster Point.

Co-op:
A player who joins a campaign already in progress does not get the War Journal or Forge progress made before they joined.
Complete all Acts of the campaign in co-op on any difficulty for the achievement "You're My Brother".

Insane difficulty:
"Today We Are Canceling the Apocalypse": complete all Acts on Insane.