I keep checklists in excel on my computer, which I modify for each trip, depending on the season and what we're planning to do. I update the list & print it out about 2 weeks before hand. Then at a casual pace, I check to make sure there's nothing that needs to be purchased, refill the travel size toiletry bottles and try to get everything in the suitcase that's not clothing. Then about 1 week ahead, I check the weather forcast and start laying out the clothes, pressing anything that needs it, and double checking the list. It always seems the last week, I am super busy as work - so it works better for me to do at least some of the packing ahead of time. If I'm on schedule, 2 nights before we leave, I try to be about 90% done - that way I can finish up the last night and get a decent night's sleep. It doesn't always go that smoothly, but we try.