It's great that you're thinking about it at that age. I'm 18 and trying to make up for 6 years of intense self degradation which included a really fucked up sleep schedule, shit hygiene, laziness and gaming sessions which could last anywhere between 8-48 hours.
If you have any acne, go to a dermatologist NOW. You want to get through topicals early so that when your acne is nuts, your derm will be comfortable with giving you accutane. 18 is a shit age to go through accutane if acne affected your confidence.
Go to sleep at 8pm, not 10, 12 or fucking 2am.
Daily showers. I personally prefer it before going to sleep, because then you're fresh and dry for the morning.
Make sure you're using proper care hygenic products. Get a good shampoo and body wash that smell normal and do the job.
Deodorant. Do not use AXE, it's shit and IT'S NOT A REPLACEMENT FOR A PROPER SHOWER. Try gillette cool wave gel, it has a normal smell(stay away from sweet smells) and works great. It's worth the money.
Don't underestimate pexpensive brand name clothing, it's better and you'll be more comfortable in it.
Oh and don't masturbate.