Deus Ex: Human Revolution is a game that combines stealth, hacking, and superhuman abilities through cybernetic augmentations.

No matter how you plan to proceed in combat (or lack thereof), purchase these augs in this order for optimum gameplay success (really only 1-3 are crucial).
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1.Hacking capture {all the way to Level 5} (Cranium)
2. Cloaking {start with just the base} (Skin)
3. Extra energy cells (Torso)
4. Conversation enhancer (Cranium)
5. Extra storage (Arms)
6. Icarus Landing System (Back)

Hacking is instrumental in getting around and uncovering loot. You should be able to purchase all the way up to Level 5 while still in Detroit, so make sure to seek out the Level 4 and 5 locks before leaving.

Cloaking is always useful as a shortcut through areas which otherwise would require precise timing to avoid being discovered by guards. Even those pursuing non-Pacifist runs can find themselves outmatched every once in a while. While running cloaked, guards may comment "I hear something" or the like but will not go into 'Hostile' unless you physically bump into them.

Extra energy cells let you take out more guards, stay cloaked longer, and use your augs more flexibly.

Conversation enhancer is essential for a few achievements, and generally makes persuasion easier through the use of pheromones.

More storage lets you keep more loot between trips to the shop, and if you've played any RPG games you'll know how key this is to building your character's wealth.

Icarus Landing System is required for one ebook in the Doctorate achievement.

Now to info on the actual gameplay of Deus Ex: HR - DC.

-Press F5 to quicksave before hacking. Try to capture the cubic Data Stores for small hacking consumables to be used on Security Level 4 and 5 locked devices. Hack everything, everywhere, and you will level up quickly; if you use passcodes provided in emails or Pocket Secretaries, you forfeit the XP.

-If going for a no-kill run to obtain the Pacifist achievement, you cannot drop unconscious bodies from deadly heights. Moving targets that have been shot with tranquilizers can sometimes kill that target, so use caution. Gas grenades will kill you, but will only knock out NPC's. Feel free to use gas grenades and gas mines to clear out enemies.

-Try to complete all Side Quests before Main Quests, because once the Main Quest of a location is finished, you leave and cannot return to those Side Quests.

-There is ALWAYS a stealthy route to any given target. You just have to look for it.

-In this new Directors Cut, boss battles now have nonlethal options, freeing you from carrying guns, frag grenades, and the Typhoon explosive system. The caveat here is that you will still be shot at by said bosses, so once your core augs are purchased you may choose to invest in Dermal Armor.

-When first given the option of taking a stun gun or tranquilizer rifle, choose the stun gun. It works instantly and guarantees one knock-out per shot, in addition to being completely silent. In contrast, the tranq rifle takes time for the dart to hit the target, and is affected by bullet-drop gravity.

-If in a stealth situation where you cannot find a feasible way to reach your target undetected, there is no shame in eating a few bars of energy to run invisible to your destination. As long as you are cloaked, enemies may comment on your footsteps but will not engage you.

-Upon visiting a new area, locate the LIMB clinic and purchase both Praxis Kits (5000 credits each). These are the single most rare and valuable item in the game, as well as the only way to upgrade augmentations. Praxis kits can still be obtained from leveling up, but this is a much slower method.

-Manually save before boss battles, arguments with key important characters, and possible decisions. There are MANY missable achievements tied to conversations.

-For the "Foxiest of the Hounds" achievement, you can be detected by the red 'Hostile' indicator, as long as no alarm is sounded. However, you will not receive the 'Ghost' mission bonus for any missions where you are spotted by enemies.

The above contains everything you need to know about gameplay, but walkthroughs and achievement guides can still be useful for getting missable achievements and finding hidden loot. Also take care not to forget all the ebooks you must view for the Doctorate achievement which is one of the career-long achievements.