Usually the modern sequel to a classic PC game ends up simplifying it. Human Revolution, however, doubles the number of different augmentations you could give yourself in Deus Ex.
It also puts more of the burden of choice on you: you can install any augmentations you have the points for, rather than just the ones you've found the right canister for.
So until you know how they all work, it's not easy to plan your character. You earn Praxis points, the level-up currency, quite slowly at first, and there are no refunds for choices you regret. So I'll talk you through the best augs, what they do, and what kind of playing styles they suit.
Bear in mind that you earn Praxis points for accumulating a lot of experience, and you get more experience for some playstyles than others. Just shooting everyone until they die, for example, is the worst way to go. Yes, you get 10 points for each kill, but that's in contrast to 100 for every alternate route and secret area you find. When you do take people down, doing it non-lethally and in one hit gets you the most experience. There's an extra 250 in it for you if you complete your objective without setting off alarms, and a whopping 500 XP for doing your job without being seen at all.
If you're interested in the talky side of Deus Ex, get the Social Enhancer aug as early as possible. It'll analyse a person's brainwaves to give you a hint about their personality. If you start losing a heated argument, you can release pheromones and exploit your knowledge of their character to smoothtalk your way out of it. Even in normal conversations, you'll get new dialogue options that lead to information or help it's impossible to get otherwise.
Whether you're planning to go stealthy, violent or both, the Smart Vision aug is amazingly useful. It lets you line up a shot on an enemy's head before he comes round the corner, or hide before he has a chance to spot you. It also highlights cameras, locked doors and computers – perfect for finding the nearest security console without blundering into every room. Then you can turn off cameras, bots and turrets, or take them over.
Two augs are specially designed to get you into secret areas: Jump Enhancement and Lift Heavy Objects. Jump on top of big things, or move them out of your way. The difference is that Lift Heavy Objects only costs one Praxis point, and it also lets you throw stuff to knock people down. That makes it the better early choice. Get the Jump aug later if you like exploring: a few jumps can't be made without it, and it's good for getting out of danger.
Best aug in the game? Reflex Booster. It makes Jensen good enough in close combat that he can KO or kill two foes at once. It happens automatically, so he'll sometimes kill a civilian as well as the guard you're attacking, amusingly enough. It still only consumes one pip of energy, and the takedown animations are hilarious. It's also a huge strategic asset: you can headshot one guard and melee another two in the same instant.
There are two ways to upgrade the energy bar augs consume: more cells, or faster recharge. Faster recharge is much, much more useful. The default recharge time is agonisingly long, and having more cells doesn't help much: the extra ones never regenerate automatically, so it's only an advantage when you consume a giant jar of cyberboost. Those are rare and bulky. Just eat cyber-boost bars whenever you need more than one cell.
A few fights suck. Don't suffer through them. Spend the three points it takes to get the Typhoon Explosive System aug and max out its damage. Don't bother buying ammo at a LIMB clinic – you get one charge free, and you'll find more lying around. Now you can run up to any boss in the game and release a swirl of explosives that will obliterate it. Some bosses take two hits, but those giant Box Guard droids only take one. And it looks badass.
A one-point upgrade to your arm aug will let you smash down any weak points you find in walls around the levels. There are actually lots of these, if you look for them, and they're incredibly satisfying to punch down. But be aware that the arm aug isn't the only way to do it. Any frag explosive will knock them down too. Since wall-punching leaves you standing in the hole, it's sometimes safer to blow them up from a distance.
There are many, many ways to upgrade the amount of information you get about where your enemies are and what they can see. One point will upgrade your map aug, doubling the radius your minimap detects enemies, and show even those you haven't seen in real life yet. The Stealth Helper aug lets you see the radius of suspicious sounds you make. But more usefully, a one point upgrade shows enemy vision fields on your minimap. A huge help when sneaking.
A cheap upgrade most people will overlook is for your eyes: immunity to concussion grenades. Enemies don't throw that many at you, but you find loads throughout the game, and they can send whole groups of enemies flying. Normally, your own concussion grenades will blind you even if you're round a corner. With this upgrade, you can knock down a whole crowd of enemies right in front of you, and skewer or headshot them all before they can get up.
There are four hacking augs, but forget about Hacking Analyse: you don't need to know what's in the nodes you capture. It's worth upgrading Hacking Capture to level three as soon as you can: that'll get you into most computers and locked doors in the first 15 hours of the game. You may find hacking gets hard on level three terminals – if you have two points to spare, Hacking Stealth will solve that. If you can only spare one, upgrade Hacking Fortify.
Hacking is all about being ready for the moment you're detected. When you click on a node, hover over the Capture option to see the chance you'll be detected. If it's more than 40%, assume it'll happen. The trace program captures everything it can on its way to you, and adds points onto those nodes, making them slower for you to take. So when capturing risky nodes, capture everything else you can at the same time to get it before the enemy.
You can Fortify the nodes you've already taken, increasing the time limit you'll have once you're detected. The drawback is that Fortifying risks detection so don't do it while you're safe. The time to Fortify is when you're capturing a risky node – again, anything over 40%. While that node captures, Fortify your starting node, and every other one between you and the enemy. You can do them all at once, and since you're going to get caught anyway, why not?