There are a few lessons I learnt over the years that I wish I learnt a lot sooner - hopefully, this is helpful to some of my younger audience.
A lot of this involves experimentation but it is particularly important to experiment because a lot of these changes can have lasting impacts on your life - eg, spending an hour learning how to communicate with your hairdressers will pay off for every haircut you'll ever get.
You don't always need shampoo
I always shampooed my hair whenever I had a shower growing up. I think this was my bad idea because my hair was always dry and 'puffed up' most of the time (which didn't look great!)
I discovered no poo and realised there were people who never used shampoo and said there were promising results, so I gave up on shampoo. My hair felt pretty disgusting after 3 - 4 weeks, so I came to only wash my hair with shampoo that often. Otherwise, I'd only wash it with water.
This seemed to make a lot more sense than using shampoo to wash off all the natural oils and then using conditioner to put on artificial oils every time you shower.
It feels a little weird at first, but I like the natural oils in my hair and how it means I can shape it and 'slick it back' without any products (which I would have to later wash off with shampoo if I used). The texture does feel a little weird because my hair always feels a little oily, but I got used to it. It also means my hair doesn't always look 'puffed up'.
Anyways, when I did have to wash my hair, my hair would puff up so I would apply coconut oil on it soon after washing it so it doesn't 'puff up'.
My suggestion is to see how long you can go without using shampoo and wash it as infrequently as possible.
Learn what haircut style fits you
I really disliked haircuts growing up because I never looked good in them afterwards - my dad always decided because I didn't know how to communicate with the hairdressers and what 'looked good' to him was different to me. My hair 'puffing up' due to frequent shampooing only made it worse.
I decided to learn how to communicate with my barbers by reading a bunch of articles and watching videos on YouTube. I also looked at a range of hairstyles on Pinterest to figure out what I liked.
I usually went to a good hairdresser and showed a picture of a haircut I liked - a picture speaks a thousand words - but I encouraged them to make changes they thought would look good on my head shape and face.
Initially, I noticed my top was cut too short and asked a few friends for their honest opinion, so I made a haircut journal of what I'd change next time until I settled on the perfect haircut for me. I always got the barber to describe the haircut back to me in words (eg, combover with X inches on the top and a Y on the sides with some thining).
After finding the perfect one, I no longer hated having haircuts and went more frequently to maintain the one I had at the same hairdresser.
I would recommend spending a little time finding a haircut that looks good on you because it greatly affects how others perceive you.
Use good face wash and face towels
If you have any skin conditions like eczema then take this advice with a pinch of salt and do a bunch of research to find something that works for you.
Growing up, I always washed my face with bar soap - this is a terrible idea! The skin on your face is much more sensitive than your hands, and it can dry out your face as the soap strips off the natural oils and can lead to more cracking and acne.
I also learnt to not dry my face with the same towel I used to dry my hands and to instead invest in a set of face towels which you change on, say a weekly basis. This way, your face stays clean for longer.
You can also go further and buy more pillowcases which you change every few days to keep your face cleaner. It seems pretty important because your face is pressed against it for almost eight hours a day! I haven't gone this far, but I probably should.
Get comfortable trousers that fit
I don't like most jeans and often wore chinos growing up, but I never found them too comfortable.
I've only tried Hollister's Skinny Jogger Pants so far and have really liked them.
Some of these can be a little pricey but given you spend almost all your time wearing trousers, doing research into a good and fashionable pair for you seems worthwhile. And given that you can return most products within thirty days trying a whole bunch seems like a good idea (do note that most stores may require you to keep the label on to return it, so check before returning). However, this may just be for the UK. Countries like Japan seem much more strict when it comes to returning items.
I'm still learning a whole bunch about fashion, so I'm by no means an expert. I found Tim Dessaint's channel to be invaluable for this - I'd recommend watching his most popular videos.