I have the -30 bag from cabelas. Its not the lightest but its necessary. I also pack my thermarest and a tarp. Usually a couple snickers for fast fuel, and some jerky to chew on. Extra set of gloves and wool socks in a ziplock. I usually have some sort of stocking cap for nighttime or when I am hunkering. Depending on the outing I'll also pack an extra shirt in case my other gets sweaty. SWEAT KILLS. I have vaseline cotton balls for a fire starter, and no less than three lighters on me. Usually one with the socks or gloves, one in the pants pocket and one in the coat.
Yes, I will secure my pack when I spot an animal and do a stalk or I'm covering a spot I want to be extra quiet in. Otherwise its usually pretty close.