Getting ready for an overnighter still starts two or three nights in advance for me. I'd like to think I'm getting better at it, but I'm not sure. There's no such thing as one universal set of krap that works for every outing - there are some universal basics, but each trip seems to have its own peculiar requirements.
Of course my dream is to be so efficient that I could pack in about 20 minutes and I'm working on that system, but it's still pretty lame, as I'm about 480 minutes shy of my goal. But still, it's a system:
I keep a master electronic kamping krap list and the starting point is to print a copy and attack it with sharpies and highlighters. That sorta serves to wrap my mind around how I expect the trip to go and what I might need.
I've centralized all my most-used krap into a few plastic storage boxes and the next step is to go through them, with the sharp focus that I obtained in the previous step, and pull out everything that might possibly be of use. This used to take the entire living room floor, dining room table, every surface in the kitchen, and several chairs. Now it just takes one basement countertop, so I suppose I can consider that as progress.
What makes packing so hard is that once you've done a coupla these, you come to the "understanding" of how just a few insignifcant ounces of unnecessary gear, here and there, can add up and conspire, and turn you into a rolling turd. So it ultimately boils down to an excercise of wants vs needs.
Which works fine, as long as you keep all your wants and needs in plain view. For the fourth time, I almost lost sight of a major need - my sleeping bag. When that eventually happens, the long and bitter night will surely be the driver of a major overhaul of the system.
For the time being, though, I'm good. Albeit slow.