I composed another answer, but somehow it got lost without posting, sorry. I see others have covered about everything. A lot depends on the type of terrain, and how long you'll be staying in one place.
Fecal matter must be well covered- that usually means buried- otherwise flies and other insects will visit it before visiting food. Backpackers are usually pretty good about this, but I've seen campers dig latrines and leave fecal matter uncovered in them while preparing food less than 100 feet away. Not good.
Most backpackers carry trowels for the purpose of digging "cat holes", there are very nice folding stainless ones that are too heavy, and light plastic ones that don't dig nearly as well. Really spartan sorts sometimes use a tent stake.
In the deep woods, I personally favor old, mostly buried, mostly decomposed logs, which in untended woods are everywhere. The soft, moist, rotted wood is easier to dig deeper in than soil, it's easier to cover and disguise afterwards, and it just adds to the decomposition process already underway.
I know from long personal experience that if I've switched to freeze-dried food for the trip, I need to be especially sensitive to any, er, impending need for the first few days, as something about the switch to freeze-dried food seem to make it go from barely noticable to EXTREMELY URGENT very quickly, and usually at the worst possible time and place. For those first days, I make sure to have TP and the trowel very handy, and be aware of my surroundings with that in mind.
In the woods, those little "travel" packets of facial tissues work fine, but because of the way they're folded together in the pack (for easy dispensing), on an exposed ridge or knob, a high wind can whip the entire contents out of one amazingly fast, before you can react. May or may not be a factor depending on where you're going.