A goal without a plan is just a wish.
What To Pack
Using A Packing List
Arguably the single most important aspect of intelligent travelling is the issue of what to pack. This, more than anything else, will determine the extent of your luggage, the weight of your load, and the state of your happiness. Your top priority, then, should be the acquisition, personalization, and use of a good packing list. "What to pack" is far too important to make up as you go along!
The notion of a "packing list", as used on this site, differs considerably from that found elsewhere. Most people think of a packing list as a list of suggestions for — or "reminders" of — items you might wish to take on a particular type of trip. If you're such a person, you'll likely find the material on this page to be quite revelatory, as that is nothing like the type of list that I'm advocating here.
Do I Really Need a Packing List?
It's not possible to overstate the importance of actually creating a personal packing list, and using it regularly. Such a list serves three important purposes:
First (and foremost), it serves as a pact that you make with yourself, an agreement (and ongoing reminder) that if it's not on your list, it's not going in your bag (because all the necessary items are on your list). This defends against last-minute attacks of "I might need this." The worst possible time to be considering what to take on a trip is while you are packing for it!
The world is awash with so-called "packing lists". Thousands can be found on the Internet, and almost any travel store will happily supply you with what usually amounts to a list of the many things you might buy from them. And therein lies the fault of most such lists: they enumerate the possibilities, rather than eliminate the liabilities. A list of stuff you might want to take is very different from a list of things that you can't travel (comfortably) without.
Even the Internet's venerable Universal Packing List is intended to be exhaustive, thus not at all the type of list that I am suggesting here (in the real world, author Mats Henricson uses a very different — and much shorter! — list for his own actual travels).
A proper packing list serves a second important purpose, one that lies at the heart of any pack-light pilgrimage: it provides you with something tangible, something you can measure. Which, in turn (implies Lord Kelvin, as quoted here), gives you something to manage, and a path to improvement. Only by studying a quantitative record of how we actually travel can we begin to make things better; lacking such, we are only making uninformed guesses, whistling into the wind.
The third function of a packing list is to serve as a checklist, helping to ensure that nothing important will be forgotten. The go-light traveller in particular is only carrying items that are essential to the journey, so forgetting one of them may be especially inconvenient. Carrying your list along with you during your travels can also be useful when repacking, by helping to ensure that you have not left anything behind. Additionally, if that list resides in your bag, and includes your (highly visible) contact information, you improve the chances of that luggage being returned to you should it be "mishandled" somewhere along the way.
Packing List Utilization
I've used my own particular list (which is analyzed in considerable detail elsewhere on this site) for more than four decades of worldwide travel. I could probably reproduce it from memory. Still, I never fail to take the minute or so necessary to check it on every single trip. And, on more occasions than I like to admit, I've been reminded of some item (like a belt for a pair of trousers already packed) that I would otherwise have forgotten. It's no coincidence that aircraft pilots are required to complete a mandatory checklist — on each and every trip — before being allowed to fly the plane.
There's a [superfluous] app for that™: You'll find no shortage of packing list management applications, generally oriented to what most people believe that they require: a variety of lists for different situations, destinations, climates, etc. In my view, those who feel the need for specialized software to manage such list(s) are completely missing the point; thinking of packing lists in this fashion is actually detrimental to learning how to travel lightly. The successful light traveller uses a single list, updated infrequently. And this can be a simple text document; if you feel the need for some elaborate, feature-rich software to "manage" it, you're making the wrong kind of list!
Don't pack items that are unnecessary for a specific trip: you're not supposed to take everything on your list! Parkas aren't needed in North Africa, nor are shorts in the Andes (for that matter, shorts are culturally inappropriate in many countries); malaria tablets and a mosquito net are unlikely to be helpful on a trip to San Francisco; dressy shoes might be dispensed with during an Amazon river trek; and you shouldn't need luggage locks when visiting your grandmother in Manchester (unless she has proclivities that might dictate otherwise). The list described in such detail on this site is intended to encompass items that are sometimes part of a one-bag traveller's needs, not always. It would be an unusual trip indeed that demanded all of them.
Finally, keep in mind that the particular packing list detailed on this site is my list, not yours. It's an example, not a directive. Of course you are both welcome and encouraged to use it as a starting point to create one that's right for you, adding or removing items as necessary to address your personal leisure/business needs. Just resist the temptation to add non-essentials. If you're thinking "I might need this", you're likely mistaken (don't pack your fears); if it's "my trip will be a disaster without this", you may be right. But consider it carefully and dispassionately. Will the joys of listening to Radio America really warrant lugging that short-wave radio? Do you truly need that 200mm lens? Perhaps, though you are unlikely to hear of someone returning from an extended trip who vows to take more stuff the next time!
But What If I Forget Something Important?
… chance favours the prepared mind.
You won't. If you follow your blueprint. That's why you have (and use) a carefully-considered packing list. That's why the pilot never forgets to turn on the window heat to ensure that the view doesn't suddenly fog up during take-off. Or turn it off when the aircraft is parked.
In truth (because she literally had insufficient time to double-check her list, and was relying on memory alone), she did manage to forget her deodorant, but it turns out that you can buy deodorant in England. We had such a pleasant trip that we later elected to move to Cambridge, where we lived for a year.
And unless you have a similar amount of time in which to prepare for such a journey, I don't expect that you'll forget the deodorant!