I've used a packing list for travel for a while now. My current method is to set everything up with checkboxes, uncheck them all beforehand and then recheck them as I pack or as I decide I don't need them for this trip.

I used to just group items by category (outerwear, electronics, etc), but now I've found it better to group items by where they're going to be packed (pockets, under-seat backpack vs carryon / checked bag).

Below that, I have short supplemental lists for things like camping, international, trips with swimming/beach, formal (wedding, etc), or trips longer than a week.

Also, a "Before You Go" list that's stuff to remember when literally walking out the door (take out the trash, shut down home theater computer, etc) that isn't realistic to pack or do in advance. Still a work in progress, but it really helps free up mental energy.