The biggest two things people can do is not be fat, which is simple, don't drink calories, cut soda, drink tea.
Ditch bread, pasta, even rice if you need large portions, or cut portions.
If you really need to snack due to shit habits, carrots and carrot sticks are great, hommus is a great healthy dip for them, celery if carrots aren't your thing.
no.1 thing dudes fuck up is skincare, it's very basic:
drink lots of water, if your pee isn't clear every time, you're not drinking enough
Get some basic sorbolene/vitamin E cream and throw that on your face after you've had a shower and before you go outside (the wind will dry the fuck out of your skin).
Lipbalm also is nice, but if you drink enough water your lips should naturally look decent if you don't lick them a bunch.
Meme diets are just that, memes, don't fall for them and just eat balanced, drink a shittone of water, you can go from 2.5 to 5 with just this if you're lucky, else, it won't hurt and you'll feel less unhealthy.
I unironically recommend a kick scooter for excercise if you live in a flat area, it's 3x faster than walking and you can skip most busses that aren't needed for long trips, fold the thing under the seat while you're not using it.
Be sure to have one with ~200mm wheels so you don't end up on your face if you hit a bump and you go at a decent speed.
lower deck to the ground = better, less sore leg muscles from kicking and bending.