at least 8 glass of water a day.
This is archaic and unscientific advice. How are we defining '1 glass' here? 250 mL?
Basically just stay hydrated, a good rule of thumb is that if your urine is a pale straw colour you're well hydrated, if it's clear you're over-hydrating which you don't want (Look up dilutional hyponatraemia, there is such a thing as too much water to the point where it can cause death).
Back on the topic of skincare though, in addition to staying hydrated this is my current regimen, subject to brand change depending on where I am in the world but I always try to use the same type of products if that makes sense:
-Nivea Men Volcanic Mud Foam Face Wash in the shower daily (contains salicylic acid)
-Neutrogena Men Invigorating Face Wash right when I wake up and just before I go to bed
-Nivea Men Exfoliating Face Scrub 2x/weekly before shaving
-L'Oréal Men Expert Hydra Energetic Active UV Defence SPF15 Daily Moisturising Lotion daily before leaving the house
-L'Oréal Men Expert Hydra Energetic Anti-Burn Ice Effect Aftershave Balm 2x/weekly after shaving
In short: stay hydrated, have a balanced diet (Vitamin A, C, D, E and biotin are important for the support of healthy skin. As the old adage goes: healthy skin starts from within), exfoliate once or twice a week, wash your face at least twice a day, use a moisturiser that protects against UVA/UVB rays (minimum SPF15 so as to have adequate defence against photo-damage) once a day and of course don't touch your face!
Other products I use that aren't absolutely necessary but have nice benefits:
-L'Oréal Men Expert Hydra Energetic 3 Day Beard Moisturiser:
Since I shave anywhere from as often as 4 times a week to as seldom as once every 4 weeks, this product is nice because it softens facial hair as well as preventing and soothing the ravenous itch that accompanies 1+ week old facial hair. I'll never go as far as growing an actual beard but at the 4 week mark my facial hair will be at the Calvin Harris/Captain Hook/Ewan McGregor level.
-Clinique Acne Solutions Spot Healing Gel:
I use this immediately after I notice I have a spot, it contains 1% salicylic acid and has been the pinnacle of my skincare regimen since I was 12.
-Clinique Clarifying Lotion 2:
This is a toner type product that I'll use after a long day of being out in the heat and humidity, basically to remove any excess oil or sweat before I go to sleep.
-Vaseline (white petrolatum USP/white soft paraffin BP):
The only time I'll use this is to moisturise my lips in the winter or to remove eyeliner (I went as, you guessed it, Captain Hook last Halloween. A message to my fellow pirates: eyeliner is important, never swashbuckle without it!)
-Molton Brown Protecting Vitamin Lipsaver:
I'll use this to moisturise my lips in the seasons prior to and following winter.
-Nivea Men Clear Effect Gel Moisturiser:
I'll use this product as my moisturiser if I have a spot or a few spots on my face (not very often, maybe about once every two weeks or so), if I know I'm going to be out in the heat and humidity (hence sweating a lot) or if I know I'm not going to be able to wash my face for a while. It contains salicylic acid and L-carnitine which reduce and hence control sebum which in turn prevents that shiny/oily/sweaty look on your face after a 10 hour flight, night out or all nighter.
I plan on replacing the Clinique gel with tretinoin in the future, as I am getting older and hence can take advantage of the anti-ageing benefit tretinoin has in addition to its original benefit of treating acne. Despite having combination skin (I get spots on my T-Zone mostly) I've never had much acne at all even as a teen (worst case maybe 4-6 small spots on my face when I was 14-16) but I'm someone who's very particular about his skin and hence am adamant about treating even the slightest small spot, which currently the worst that will happen is I'll get maybe 1-3 spots every once in a while.
That being said, many people compliment me on my skin and ask me what products I use even back when I was only using face wash twice a day and Clinique gel (I was an enigma in high school as people were always perplexed as to why I never had the classic teenage 'pizza face' acne like most of the kids my age), I've only recently (2 weeks ago) started to use the other products and have noticed a marked 'glow' type radiance to my skin, even some of my friends made comments on the difference (some people even thought I was wearing makeup LOL)