I generally use a modular approach, and usually based on Doug Ritter's PSP. I add water purification (Aqua-Pouch Plus from Survival Kit Component Specialists) and shelter always (Heat Sheet and poncho). The poncho can be clipped onto my bag or belt. I may carry more fire making tools and signaling tools as well. I will carry the survival necessities on my body (pockets) and other things in a fanny pack or day pack. Even when I am backpacking, I have a small packable day bag which I can pull quickly and go with. That is also where I keep my trauma kit, the basic first aid kit is usually attached on my backpack.

All that and dressing properly for the activity and carrying enough water for myself (and usually others) and I am prepared for just about anything.