We all know that packing for a trip is one of the most stressful parts of leaving - you think about what you'll need for weeks, how you're going to get it to your destination and you'll stress about forgetting something until you realize what that 'something' was. Compounding the stress of packing is the length of trip. Of course packing for a weekender or a week long vacation in the tropics is one thing. Backpacking for multiple weeks or months is another, especially when it is your first time.
Having a very finite amount of space is stressful. I know, because I have packed for backpacking trips multiple times and it is ALWAYS on my mind for weeks beforehand. Even now as I am preparing for my next trip, I am not sure how I am going to get all of my gear overseas. It always comes together though, and I have learned a few things over the years.
Packing more than a carry on adds up very quickly financially, so if it can be avoided at all, downsizing should be considered. This will depend largely on whether or not you plan on taking multiple flights during your trip as well. If you plan on flying often with all of your gear, consider packing a backpack only and avoid the checked baggage fees. You also get to skip baggage claim when you haven't checked a bag, which is meaningful considering the time you save not waiting and the lesser chance of you losing your own baggage. If you have a home base on your trip and will be able to leave a suitcase there, then being a little less anal about what you allow yourself to bring is probably just fine.
If you are planning on bringing a backpack only, consider getting yourself a Pacsafe pack. I have a VentureSafe EXP45 Econyl ® Anti-Theft Carry On pack and I have genuinely loved it. I believe it is the largest size allowed as a carry-on on most airplanes, has numerous anti-theft features which are awesome and loads like a suitcase. The anti-theft features are wicked when you are hosteling all of the time and I can't say enough for the way it loads! My hiking pack is a top-load as are 100% of the backpacks I have seen fellow travelers with, meaning that it has an opening at the top of the backpack to pack your gear, much like a regular day-use backpack. My Pacsafe bag allows me to unzip the whole thing from top to bottom to reach everything (again, just like a suitcase), avoiding situations like one of my best travel buddies when she had to unpack her whole life in the airport to get at something at the very bottom of her bag that wasn't coming out any other way. Long story short - I am a huge proponent of these Pacsafe bags and would definitely say mine was worth the money for the added ease and space.
One thing to seriously focus on while packing is: ONLY PACK THE ESSENTIALS. I say this because the first time I went on an extended trip, I packed far more than I was ever going to need. Most notable is to leave behind all of those outfits that you own that you may love but that you almost never wear. They are great, but if you bring things that you are rarely going to wear, they add a ton of weight and space in your suitcase or backpack that just isn't worth it. I was guilty of this, and my closet at my flat in Scotland was full of clothes that I only wore once or twice. I was usually wearing that same few items all of the time.
Something else to consider is the seasons you are going to experience. Do some homework on the typical weather for the time of year you are travelling and pack accordingly. I would caution you to rely too much on the experiences of others. Most folks usually only visit a place for less than a week, and that is just not a reliable experience to bank on when you are packing for multiple weeks or months of travel in a given area. I remember I was cautioned about the rain in Scotland more than anything before I left, but this was based on the brief experiences of some folks and the stereotype of the country. What I found while I was there was actually that the wind is what you need to watch out for, forget the rain! I was prepared for monsoons in Scotland, but what we experienced instead were constant, bone-chilling, powerful winds and likely less rain that what I grew up experiencing in the Pacific Northwest. My point is - read up well on your destination and truly try and know what to expect. Advice from friends and family on their experience is super helpful in some situations, but it is not always accurate when it comes to things such as your predicted weather report.
So what should you pack then, you ask? Pack a few basics that you can mix and match. These will differ depending on the time of year you are travelling in and where you are going, but the premise is the same no matter what. Bring less than five t-shirts and a few pairs of jeans that you are comfortable in and will wear constantly. Bring one jacket and one sweater. Bring three pairs of shoes or less. The multiple options just aren't necessary when you are on the move all of the time and when space is precious! Shoes are a big part of this - you are likely to only wear your most comfortable and versatile shoes while you are out and about. Wherever you are, you will likely be walking for miles and won't wear those heels that you 'had to bring'. I was definitely guilty of this in the past, and have only learned to restrict myself after I carried two extra pairs of shoes all over Italy that I didn't wear once. Cobblestones and high heels don't mix, and they're just not comfortable for distance ladies. If those shoes ain't made for walking, leave them at home!
If you are gone for more than a few months, packing a back-up duffel for those things you will acquire along your travels might be a good idea. Souvenirs, new clothes and memorabilia you collect along the way adds up, and you don't want to leave anything behind! On long trips I bring a back-up bag that is empty and folded in my backpack or suitcase that I pack up for the trip home.
Lastly, a good move is to keep a list on your phone or somewhere else that can be accessible to you as you think of things in the weeks prior to your departure. You will think of random items you need to pack as you are out and about, and keeping a list of them as you go will help with the "I forgot something" anxiety. Ultimately, it is highly likely that you will be going somewhere where you can buy those things you missed or didn't realize you needed. If you are indeed going somewhere more remote, consider using plastic-less products from Lush. The solid shampoos and conditioners are by far the best products to use when you are travelling, being on the lighter side, small and waste-less.
Happy packing folks! And wish me luck with mine...