#1. Weigh everything - including yourself
In order to make the right decision about what gear to take on a trip it's imperative that you weigh everything and record it - that not only lets you know which of your two bits of similar gear are the lightest but it also enables you to track your total pack weight as you swap in and out different pieces of gear.
If you know your way around a spreadsheet - even better, because adding up all the weights is then done for you. Having sight of your total pack weight enables you to make decisions about what luxuries you can take without going over your target weight.
#2. Go on a diet
It's all very well saving a few hundred grams by buying a new, lighter sleeping bag but you can save kilograms by going on a diet - losing extra weight before a trip can often be the best way of ensuring you are carrying less weight and reaping those benefits. Of course you may be at your fighting weight already - in which case its back to the kitlist!
#3. Take less stuff with you
This is a great way to save weight as its not simply getting a lighter version of something - its actually saving the whole weight of that item. One way to do this is to look at the gear from previous trips and see if you used it - if you didn't then it perhaps could be left out on your next trip.
Caution and a bit of common sense is required here though - I haven't used my first aid kit for a number of trips now but I'd always take it with me - for obvious reasons. Similarly if there's a chance of needing an ice axe and crampons don't even think of leaving them at home.
But, do you really need a spare pair of trousers as well as shorts? How about those shoes for the end of the day, did they earn their place in your pack?
#4. Buy lightweight alternatives when you come to replace your gear
There's always some piece of kit that needs replacing - when it comes to it weigh the item you're replacing and look for accurate information on the weights of the potential replacements. Weight doesn't have to be the main factor you take into account in choosing replacement kit but if you consider the weight you're much more likely to get a lighter piece of gear than the one you've already got.
It's also not a good idea to go simply for the lightest by default - the lightest may not be as robust as you need or have the features that you like - but if two similar items meet your requirements go for the lightest.
Sometimes it's hard getting accurate weights for everything so I'm going to give our own website a plug here; we weigh everything in every size - even our suppliers refer to us for accurate weights as often the weight quoted on a manufacturers website is the weight of a pre-production sample, which may not be correct. Our weights are correct because we've checked them when the item first arrives.
#5. The big three - Tent/Sleeping Bag/ Sleeping Mat
If you intend to replace kit in order to shed weight then there are some key areas where the biggest impact can be made. These are the big three. By replacing one or all of your tent, sleeping bag and sleeping mat will probably yield the biggest weight reduction in your kitlist.
The very lightest tends to be the most expensive, but if you have a limited budget it may be possible to identify compromises that will still save considerable weight without compromising comfort.
Tent choice - You could go for single skin which offer better volume to weight ratios. Trekking pole tents save the weight of the poles. Or just go for the ultralight versions of traditional designs.
Sleeping Bags - If you're currently using a synthetic bag then a lot of weight (and packed volume) could be saved by moving over to down. Down bags have a much higher warmth to weight ratio than synthetic and can be compressed into smaller packages. They are more expensive than synthetic but also last longer.
Sleeping Mats - Ultralight Airbeds are currently the most popular mats, they are lightweight with small packed size and really comfortable. Most are also insulated - an insulated mat makes your sleep system work harder, with a highly insulated mat you can use a lighter weight sleeping bag and still be warm.
Rucksacks are a special category because they don't serve any purpose other than to carry the other stuff you need - they should be as light as possible consistent with being comfortable and convenient to use.
Over the years features have been added to rucksacks that you don't necessarily need and have added to the weight of the rucksack until it could easily be the heaviest item you're carrying.
In the lightweight world if you carry less stuff you'll need a smaller lighter rucksack to carry it in - thus saving more weight - the harness on the rucksack doesn't need to be elaborate - thus saving more weight. I can go backpacking for a month with a 60 litre rucksack - or smaller - that weighs about a kilogram - many so-called backpacking rucksacks weigh twice this amount.
There's another spinoff benefit from taking less kit, you're more organised, there's less kit to find a home for and it just seems easier to find the item you want.
Footwear is another area that's been over engineered in my opinion, adding weight to your boots. Heavy boots may be required for crossing a glacier or high altitude mountaineering but most of us use paths, walk at relatively low altitude in reasonable weather.
Companies like Inov-8 have paralleled the growth of trail running and mountain events and have been producing ever lighter footwear that can cross over into the trekking and backpacking world. Their success has prompted more traditional outdoor footwear manufacturers to examine their ranges and look at producing lighter weight versions of their traditional offerings.
The old adage about a pound on your foot is equivalent to carrying 3lbs on your back is true and choosing lighter weight footwear can be a good way of unlocking your lightweight potential. Most of all your footwear needs to be appropriate to the activity you are doing - but with experience you get to know what you need.
Here's an example - I'm doing the Chamonix to Zermatt route this summer, backpacking it and taking 10-14 days. Look in any traditional boot manufacturers catalogue at backpacking footwear and you will see heavyweight boots with stiff soles. I will be taking walking shoes, not boots, they may not even be waterproof, but they will weigh half of the backpacking footwear that's categorised as such. From experience I know that my choice of footwear is appropriate to the trek I will be undertaking.
Water is heavy, typically you may need 3Litres during a warm day in the summer - that's 3kilograms if you carry it all from the start, a figure that drives a truck through your efforts to save 30grams on your choice of headtorch!
The answer is to research your route - if there are water sources that can be relied upon along the way then here's your opportunity to save weight - if there's a source half way along your route you only need to carry 1.5litres - you've saved 1.5kilograms already. If there are four water sources spread throughout the route you only need to carry a litre or less - saving yet more weight.
Most organisations recommend water is purified before drinking, but this needn't add weight if you use tablets - Micropur tablets weigh about 5grams for 100 tablets. If you're travelling to a country where water may be full of particulate material only then will you need a filter.
There are no compromises here - food weighs a lot - you will probably need to carry about a kilogram of food for each day. But even here a bit of planning can take the weight off. If there are re-supply opportunities along the way then there's no need to carry everything - plan to buy supplementary items along the way so you don't need to carry as much.
Freeze dried meals weigh much less than other foods for their calorie content, they're not the worst but they don't taste that good and personally I couldn't live on them exclusively. However its useful to weave them into your diet - so, if you're doing a trek which requires you to carry a weeks worth of food then make up about a third of it from freeze dried meals - striking the balance between weight and satisfaction.
A final top tip on food is to eat the heaviest items first - sounds obvious but not everyone does it.
#10. Wear stuff on the plane
It's tempting to have a set of clothes for travelling either side of your trek - don't do it. Wearing your trekking clothes on the outbound journey makes no odds to anyone except yourself when you shoulder the pack to start your trek.
The journey home can be quite different - clothing ingrained with the sweat and dirt of two weeks trekking needs washing before you mix with other people - but that's not always possible at the end of your trek, so sometimes you have to bite the bullet and buy a clean shirt or pair of socks. Either buy the cheapest or something you'll wear again.