I usually apply this "technique" regardless of going
abroad for a whole year, whole month or even just for the weekend. I start by making a check list of things I MUST take with me.
þ Tooth brush
þ phone charger
After I have done my check list, I count the days I will be away and decide on how many pairs of bottoms and tops will I need. You will always need more tops than bottoms. If I go on a weekend trip, I usually just take one pair of pants, and probably three tops and one jacket that would go well with all three tops. However, in case I am going somewhere for a longer period of time, I always plan outfits with pieces of clothes that I can mix and match (therefore creating more and more outfits with the same pieces). I have learned that regardless of how much we lose that jacket, if it only goes well with one particular outfit than it is not wise to take it with you! We can wear that one later... Creating the outfits definitely takes longer than just packing whatever you have in front of you but it will definitely make your life at the destination easier and you will definitely be less prone to overpack. I always count the days I will be away, and do a maximum of two outfits per day (day and night) but of course always mixing and matching!
Other than this, packing becomes very easy! Don't take large bottles (suncreens, shampoos etc). Just get a little one which you can fill and it becomes much more lightweight and saves a lot of space. Once thing I have definitely learned too is that rolling your clothes definitely saves up some space IF you are travelling to a hot place (rolling shorts, tank tops, light jackets etc) because if you try to roll thick sweaters, proper jeans, and heavy jackets... it will just make everything extra fat!
So basically this is what I personally do to try and avoid overpacking or packing the wrong items! We all know there is nothing more frustrating than having a heavy suitcase and still not know what to wear for dinner!