Well, that certainly seems to be the biggest thing you can control as a passenger. Dress for the weather and pack your jacket/coat under the seat in front of you not in the over head compartment, so you can actually get to it to take with you. You have no control over how the plane goes down and very little over how the crowd reacts. Of the items you're still allowed to carry on airplanes now, your clothing has the most potential to save your life immediately after a crash. Even if you aren't facing hypothermia, clothes can be improvised into tourniquets, bandages, slings and bindings for splints.