How do you stealth in MGS5?

[foodfather]

ClassicGamingWizzz said:

I am trying so hard to get S ranking in every mission , at first it was easy, you arrive, mark them all, put ALL to sleep, go to objective and get that juicy S ranked. But now ? those motherfuckers now use helmets and some serious protections, cant put them all to sleep anymore and have to be much more creative.
I only have the horse, my dog is missing and i dont see him in ages, quiet in a cell sunbathing and listening to music and i am all by myself.

Main missions i go sealth and  in the Side Ops i go rambo style.

Going rambo is so much fun, you fucking reach a high point, sniper like 5 or 6 of those pigs and when they see where you are its time to slaughter, you call the attack chooper and that shit makes missiles and bullets rain in them while i am on the top of a builting with grenade launcher or rocket launcher cleaning the rest.

Ah, a headshot to the helmet will stun them for a good few seconds, making it easy for you go go up them them and RT/R2 their ass. As long as they are stunned and nobody saw you, it wont count as a ''detection''. 

Aslo, smoke grenades are very important for slipping by the enemies. AI sightlines are rediculously accurate, but the AI it self is really dumb.