Different view than Kevin. If you have played the other Gears and if you finsihed any on issane than I suggest doing it as your first play thru. I did the campaign on Hardcore and took my time and got all the collectables also. While doing it this way probably added several hours to my first play thru(plus to find my way in a few scenes I got hung out to dry or moved faster than the AI leaving me exposed) I found it very satisfying yesterday when these all popped up.
Keys: cover, cover and more cover. I noticed in this version that the muzzel flashes plus my higher use of grenades meant that I didnt always pick up on the on-screen damage indicator due to the busyness of the graphics. On some of the hectic firefights or when scoping in I found I suffered from tunnel vision and "looked "thru the damage indicator more often than in the previous 2. Hope that makes sense...
Dont trust the AI, I did play this playthru solo, I suggest co-op if you can, especially for the final battle. I was hanging back w the hammer and got shot in the @ss too much cause my a.i. teammates moved further down and wouldnt always respond. I also noticed that to get them to revive me that I ahd to crawl on a direct intercept path cause they would over run me if they respond at all.
Grab ammo whenever, sometimes it gets thin so grab early and often and dont hesitate to switch guns even if you have a cool "skin", bullets are better than bling. I carried a Lancer and Hammerburst a large majority of the time and swapped the Hammerburst for a limited large weapon from time to time however I did rely on firepower over style.
Worry about executions later, concentrate on survival, the Locust seem more prone to flanking and I noticed chainsaw and executions up'ed my chances of being flanked.
Hope that helps, enjoyed the campaign a ton and felt very satisfied finsihing it solo on Hardcore, debating on a solo insane but not sure if my nerves could stand the AI again at that level.