The physics of packing
As someone who is used to flinging clothes without folding, I have had to lick my wounds on this one. Without going into the physics, there is less surface area for clothes that are tightly folded compared to a rush and crush job. While the weight capacity will be the same it may assist in the amount of actual items you can pack.

Prepare
Show some foresight and anticipation about what the trip ahead entails. If you are heading to a milder climate, then maybe you should think twice about the leather jacket. If you are heading to a place in which you have no idea what to expect, check out some photos and get a sense of what people are wearing and read what other people have said and experienced about the place to give you a gauge.

Re-use your clothes
While I appreciate that you're on holidays and want to step away from the everyday humdrum, some things are worth doing and are really not that onerous. It's not hard to wash essentials like shirts and underwear. A travel-sized washing liquid can take up less room and size than a 12-pack Rio undies. Besides, it's not hard to find a local laundrette or use the hotel's washing facilities.

Keep an eye on the ladies
While at risk of being on the sharp end of a stiletto for generalising, women are probably guiltier of over-packing than men and seem to require a different outfit for each day away which is neither practical nor wise. Practical in the sense that knee-high boots may be the 'Bee's Knees' in Sydney, but they are not going to make the mustard in cobblestoned Prague. And risky in that dressing like a tourist means that you will inevitably get treated like one and a target for scams or overpriced experiences.

Monitor
If you have a partner who is a chronic over-packer, then it pays to keep a vidual on their packing movements. Trust me when I say investing an hour in "packing together" compared to a few weeks of lugging ridiculous amount of luggage is well worth it.

Sporting equipment
If you're conscious of weight restrictions, you'd be comforted to know that many airlines do not charge excess baggage for sporting equipment. As that is the case, see if you can pack as much luggage in and around your sporting equipment as possible. Besides from reducing your check-in luggage capacity, any access clothes that are thrown into your ski or surfboard bag, are also creating a buffer from any potential baggage handler that wants to use it as a cricket bat before throwing it into the plane's underbelly.

The other option, which can improve your flexibility and comfort in getting to your destination, is to rent at the other end. Although, this is an individual decision, it might make for a more enjoyable and hassle-free trip.

Presents
If you're cheap like me and try and stay with mates to save on accommodation expenses, it is also in good form to provide your hosts with a gift as a token of appreciation. Apart from simple good manners, it doesn't hurt your chances of getting a repeat call up. However, packing a present abroad can be cumbersome as well as heavy and in some instances more expensive. Again it pays to have some foresight in this regard. It might be worth investigating the option of mailing presents ahead of your arrival or if the exchange rate is in your favour, purchasing items online and mailing them locally to your end destination.

Buy stuff when you get there
Rather than have all your possessions already accumulated at the start of the trip, can you not pick up things along the way? Apart from reducing the time that you have with heavy luggage, it also encourages you to get amongst the local markets and sample new things. It may also broaden your taste in clothes, although it can also be a double-edged sword. My brother, for example, picked up a Sherpa poncho in India and I'm not convinced that's helping him back in Sydney town as much.

At the end of the day, it comes down to personal preference, knowing how you like to travel and what your priorities are. However, given all the adventure that's inevitably ahead of you, isn't it better to be focussed on the good times rather than whether you need to pack a pair of knee-high boots?