There are 90 million ways to make sure an item doesn't get left behind, and sometimes, just sometimes, it's worth employing two or three methods to make sure everything gets packed.
Falling into the simple but effective category—as the best things oft are—perhaps one of the best ways to make sure something isn't forgotten is to email yourself the missing item in the subject line.
Sure, writing things down on a packing list will get 80% of those items covered. Most of the remaining items can be remembered by physically placing remaining items in a highly visible, obvious spot the night before. But for "out of sight, out of mind" items, we've always find a quick email to ourselves works the best. (But only if you're a religious checker of email.)
Proof that we're more addicted to our devices than we'd like to admit.
Because when you've been on the road and changing hotels every night.... the last thing that you'll remember is the room number, much less than the cheese that got left in the minibar.