The day on which one starts out is not the time to start one's preparations.
How To Pack It
Useful Packing Tips
If you've done a good job of selecting what to pack, the task of actually packing it should be a fairly straightforward one (most difficulties are the result of the former, not the latter). Aside from suggesting that you pack larger items before smaller ones, there's not much I can say about the packing process itself: it's very much a function of the size and design of the bag, plus the specific items being carried on any particular trip. Some folks have good spatial visualization skills, and pack very well; others have to work a bit harder at it. Fortunately, one benefit of developing your own personal packing list is that you don't need to keep (re)solving this problem every time you pack!
All that said, here are a few ideas that you may find helpful …
Organizer Pouches
An excellent item that has become more difficult to find of late (since Outdoor Research ceased production of their fine versions) is the "organizer pouch", a flat, rectangular, often multi-compartmented, nylon bag with zipper closure(s). They sometimes incorporate see-through mesh panels, and are available in a variety of colours. These are terrific for avoiding what could otherwise be a cluttered mess in your bag, and make life easier for security inspection folks as well (always a good idea). Use a little thought to organize your belongings into categories, and store them in the pouches; this approach also makes smaller items less likely to be lost or forgotten. Cartom Products manufactures four sizes of good, basic, single-compartment pouches with mesh fronts (pictured at right); they range from 5 × 7 inches (13 × 18cm) to 14 × 18 inches (36 × 46cm).
The seriously budget-constrained could use heavy duty Ziploc® bags for this purpose, but I have always preferred the convenience and durability of nylon pouches, and they are not an expensive item. By way of example, one of my pouches contains all of my laundry-related items (i.e., sink stopper, detergent, spot remover, viscose towel, travel clothesline, inflatable hangers).
An appropriately-sized organizer pouch also makes an excellent core object for the bundle wrapping method of packing clothes. Cartom's large-sized pouch (the red one in the above photo) is well suited to this purpose, as is the multi-compartment, equally large-sized "Deluxe Pocket" (made by On Sight Equipment, and pictured at left). Both of these pouches are about 10 × 14 inches (26 × 36cm) in size; the latter version comes with tabs/clips in the top corners, which might better be removed for use as a core object.
Avoid overly-large-sized pouches (as they encourage you to fill them), and if you use more than one, ensure that they are differently coloured (facilitating easy differentiation).
Packing Cubes
So-called "packing cubes" may be something of a misnomer (they are rarely cubes, but rather rectilinear zippered fabric containers, often with mesh panels to reduce weight and make the contents visible), but they, like the above pouches, can be very helpful to organize the contents of one's bag. Your choice of cubes will depend on how you choose to organize things; fortunately, they come in a wide variety of sizes. I normally carry two, adding a third for business trips.
The first, used mostly for toiletries, is a Pack-It® Quarter Cube (from Eagle Creek, and pictured at right). A mere 7.5 × 4.5 × 2.5 inches (19 × 11 × 6cm) in size, it is dwarfed by the giant "Dopp kits" (and worse) that many people seem to consider necessary for this purpose. But mine quite handily holds all of my toiletry kit, plus vitamins, medicines, etc. with considerable room to spare. And its 300 denier poly micro-weave construction adds only 2 oz. (57g) of weight for its 75 cu. in. (1.2L) of storage space.
You can reduce even that weight, if you are willing to spend a bit (about 50%) more, using Eagle Creek's newer "Specter" line of cubes, made from extremely thin, translucent white, ripstop Silnylon. Their Specter Quarter Cube (seen at left) is dimensionally equivalent to the regular model, but weighs a whisper-light 0.6 oz. (16g).
I also employ a Pack-It® Tube Cube (also from Eagle Creek) to carry miscellaneous items, things that don't logically group in other ways (such as my flashlight, Jakstrap, whistle, compass, alarm clock, sunglasses, eyeglass retainer, water cup, garbage bags, etc.). This bag is 13 × 4 × 3 inches (33 × 10 × 8cm) in size, weighs 3 oz. (90g), and fits neatly along one side of my carry-on. Sort of my "junk drawer".
On business-related trips I additionally carry a small see-through packing cube to hold miscellaneous laptop gear: power supply & cord, cube tap, mouse, network cables, flash memory card adapter, earphones, and a remote control for presentations. The Cable Management™ 10, made by Think Tank Photo (and pictured at right), is a good choice for this usage; it measures 7.5 × 3.75 × 2.25 inches (19 × 9.5 × 6cm), and carries a lifetime "no rhetoric" warranty.
As with organizer pouches, eschew large packing cubes (that's what luggage is for) or multiples of the same colour.
The use of packing cubes (and organizer pouches) also increases the likelihood that your belongings will remain tidy and well organized should you be singled out for a bag search.
Coping with Shoes
If you're packing shoes (in addition to those you're wearing), consider the use of shoe bags: lightweight, inexpensive, drawstring bags designed to keep any residue of Parisian streets away from the rest of your belongings. Magellan's sells nice ones. A posher approach comes in the form of tailored neoprene Shoe Socks™, which eliminate the annoying drawstring, leave the shoe opening more accessible for packing things inside, and come with a lifetime guarantee, but are also costlier, bulkier, and heavier, a medium-sized pair weighing 4.4 oz (125g), compared with 1.7 oz (48g) for the Magellan's bags. Or consider the budget solution: a pair of the plastic bags in which (many) newspapers are delivered: they're sturdy, long, not too wide, weigh 0.3 oz (9g), and when their days are done, you can simply dispose of them. Some hoagie/sub/hero sandwich bags can also be used in this fashion, and in a real emergency, the free shower caps dispensed by many hotels can be called into service as well.
Shoes are perhaps the most difficult items to pack, given their typical weight, bulk, and awkward shape. Minimize the number you take, and try to wear (rather than pack) the heaviest pair when reasonable. It is usually best to pack a pair of shoes tightly together, soles out, with the heels at opposite ends. Also, don't neglect the spaces inside your packed shoes: they're great for fragile items, or anything else that will fit, for that matter (small, loose items like jewellery are best grouped in small plastic or fabric bags to keep them from rattling and/or wandering off).
Sorting Out Souvenirs & Gifts
In my view, the very best souvenirs are friendships, photographs, and fond memories: those who travel lightly are not typically looking to add more stuff into their lives. If you feel the need for something more concrete, though, or can't pass up a flea-market bargain, you might want to put some thought into what to get, and how to get it home (or haul around with you).
Locally-produced items tend to make the best mementos: "Made in China" is fine if you're visiting that country, but it's otherwise suggestive of a lack of imagination. If you're in Belgium, think lace or chocolate; when in Ireland (or Portugal), think hand-knit sweaters; and so on. Functional souvenirs are usually preferable to purely decorative ones: clothing is often a good choice, and can even replace something you've brought. Readers will appreciate local books on topics of interest, and music-lovers should consider recordings of local musicians they've enjoyed.
I always leave some space in my bag for gifts, souvenirs, and other items that I might want to bring home. Should that prove insufficient, I have the option of using my daypack or lightweight duffel to carry additional stuff. On an extended trip, I will mail items home.
Buddy Packing
If you have an extremely compatible travelling partner, you might consider packing half of each person's things in the other's bag. That way, in case of a bag being lost (much less likely for the carry-on traveller), each of you will still have half of his/her stuff. This method does, however, have the downside of providing something in the way of a disincentive to pack minimally!
Whether or not you do buddy packing, it should be obvious that when two or more travel together, many of the packing list items (alarm clock, guidebooks, repair supplies, etc.) need not be replicated for each person. And those who are similarly sized and gendered have access to far more wardrobe items!
Miscellaneous Packing Thoughts
A place for everything and everything in its place.
Whenever I check into a hotel or the like, one of my first actions is to completely clear at least one horizontal surface (desk, table, dresser top, etc.), and place all the removed clutter out of sight, often in a drawer. I then use this cleared area for any non-clothing items of my own that must be unpacked. That way, when I prepare to depart, I am unlikely to leave something behind because it "disappeared" among a bunch of sight-obscuring oddments.
When you're packing (as opposed to wearing) inclement-weather gear, and there is the slightest chance of such weather occurring, ensure that the gear goes in an easily-accessible part of your bag: you don't want to be caught in a downpour, unwrapping a clothing bundle to get at your poncho or rain hat.