Sneaking around restricted enemy grounds and taking out any hostile that comes near isn't my idea of a fun job, although that is a very good theme for video games. But we must know what it's like to be in the real thing: To be trapped in some terrorist lair, with the extremely dangerous task of acquiring crucial and confidential data deep within the bowels of its innermost fortresses, out of hostiles' reach. Charging in with guns blazing is out of the question, so that's when being sneaky and cunning really comes to good use. But the problem with stealth is that once you get spotted, your vulnerable body will be pumped full of lead and you'll just be another body of a foolish soldier who tried to unsuccessfully infiltrate terrorist HQ (of course, unless you actually manage to escape all those flying bullets and disappear into another part of the lair and get the enemy to continue their frantic search for you).
TIPS (this bit may not be totally reliable, as I take this part's sources from video games, but that's pretty much where all this post's sources come from)
Things you'll need in stealth mode:
-Silenced pistol (a normal un-silenced pistol will trigger instant enemy attention)
-Black suit (obviously black is the best color that blends in with cover, and it's cool too)
-Soft-soled shoes (For treading around silently in the shadows. No matter how silent you try to be, you'll still be detected if you don't use the correct footwear, say tap shoes)
-Night vision goggles (for the night. Otherwise, you'll be as blind as a bat, only without the sonar)
Techniques you'll need to use:
-Silenced eliminations (when near an enemy, don't shout "YAAAAH!" and pounce on him like a rabid bloodhound. For a non-lethal takedown, strangle him into fainting. For a more cautious approach, use a knife for a more fatal silent elimination. Don't try this at home)
-No explosives (too loud, use only when it could be drowned out by another sound)
-Most importantly, constantly try to make up back-up plans if Plan A goes wrong.
Silent takedown from Hitman