I have a list that stays on my cellphone that includes the basics of what I need to bring for me and for E (the hubs packs for himself). I hand write that list onto an 8.5 x 11 paper that I've folded in half length-wise (one side for E, one side for me). I like handwriting it so that I can mark stuff off, add more stuff and carry it around the house while I get stuff. I try to organize in categories: 1) clothes/shoes 2) bath stuff/makeup 3) accessories 4) other necessities (camera, laundry detergent, toilet paper, etc). E's list is a similar format with an added category for sleep stuff and toys/snacks.
So here's my thinking. I think through each day and what I need. Do I need something to wear during the day and at night? Then I make a tally of number of shorts I'll need and number of things to wear in the evenings (dresses) that I'll need. I'm an over-packer, but I'm always prepared.
The below lists were my lists for Charleston. I ended up not wearing one of my dresses and that's all! E came back with several clean outfits, but with kiddos it's better to be safe than sorry.
The other thing I do as I pack is circle things that I need to remember to pack last minute (hair dryer, E's monitor, a pair of shoes I might be wearing the day before, etc.). I've found that if I circle these things then I will definitely see them.