I have a lvl 50 Demon Hunter. Let me teach you how to be a pro. Once you hit level 45, demon hunter just gets so damn powerful and literally invincible.
I have posted each skill below followed by which rune you should use in brackets. I will then provide an explanation as to why this is the most effective build.
I have also set 2 builds you should use, one before level 45, and one after 45 due to the newer runes available.
You will notice that under Devices (3rd skill), I have switched on ELECTIVE MODE (options ----> Gameplay ----> tick elective mode), allowing me to slot in whatever skill I choose.
Note that this build is aimed to deal the highest amount of damage possible, at the same time providing you with superior survivability.
Note that this build is mainly used during the process of completing missions and NOT fine-tuned for fighting bosses, feel free to adjust your skills for single target damage when fighting epic bosses.
Pre 45 Build
Primary - Hungering arrow (Scatter Shot) - Provides extra AOE damage due to the 3 way arrow split.
Secondary - Elemental Arrow (Frost Arrow) - equivalent to the wizard's "disintegrate", best skill pre level 45, rune provides +170% dmg to every single enemy passed thru + slow.
Defensive - Smoke Screen (Lingering Fog) - Skill explanation doesn't actually tell you that you turn invulnerable. Lingering fog provides you an additional 3 second invulnerability, total of 5 seconds being invulnerable. Higher cost of discipline, but no cooldowns, it is a very fair trade. Absolutely OP.
Hunting - Vault (Tumble) - Equivalent to Vayne of the league of legends, this skill makes Demon Hunter THE king of kiting. Tumble like a boss away from your enemies when they get close, and continue to wreak havoc. The rune lowers the discipline cost of a 2nd vault within a short amount of time. If you can't juke, don't play demon hunter.
Companion (Bat Companion) - Prior to my noobness I did not realise you can use Elective mode to swap in any skill you like to fully utilize the awesome customization of skills (Toggle it under options ---> Interface).
Originally, I rarely use any 3rd skills; evasive fire is just pointless when you have vault; fan of knives is stupid because you are not meant to be a melee or get close to enemies for all that matters; spike trap is alright but the 30 hatred cost is just stupid when you have Multishot as your 4th skill. So all thats left is Sentry, which is like the Wizard's Hydra. It's alright as provides you with some extra damage. I still rarely use it UNLESS I AM SOLOING DIABLO when i kite around him and it is just funny watch my sentry dealing damage while i run in circles.
Now that my noobness has been eradicated, I use Bat Companion due to the awesome Hatred regeneration, along with the extra 54% weapon damage my baby bat deals this skill is just sick. More trolling with my extra hatred? I WILL TAKE IT!
Archery - Multishot (Fire at will) - A Godsend when you see angry mobs charging at you. The rune reduces cost to 20 hatred, meaning you can spam it for "165% x 2" as a MASSIVE AOE at a massive range in front of you. Deals insane damage. You might ask, why not Rain of Vengeance? Main reason is because enemies DO NOT STAY STATIONARY and continued getting showered when you are juking around; the second you cast it and juke away, who will you be dealing damage to?
Post 45 Build
Primary - Hungering arrow (Scatter Shot) - Same reason as above.
Secondary - Rapid Fire (High Velocity/Bombardment) - Both deals more damage overall compared to Frost Arrow. High Velocity provides you with 40% chance to shoot through enemies, meaning it is pretty much the equivalent of a frost arrow BUT + 228% dmg instead of 170%. Bombardment deals some crazy mini AOE damage, 276%. Both are viable options, yes please to that extra damage.
Defensive - Smoke Screen (Lingering Fog) - OP is OP.
Hunting - Preparation (Focused Mind) - This skill, combined with Lingering Fog, is what makes you invincible. I usually only use this when i fight harder enemies. You start a fight, when enemies come towards you cast Smoke Screen to lose aggro and continue shooting at them. Cast smoke screen again if enemies move towards you again. THEN you cast preparation if you STILL are trying to kill whatever it is you are killing. This will regen your discipline overtime ALLOWING YOU TO SPAM YOUR SMOKE SCREEN AS INVULNERABILITY for a few extra times. Like I said, OP demon hunter, is OP.
Companion (Bat Companion) - Same reason as above.
Archery - Multishot (Fire at will) - Same reason as above.
Passive
Tactical Advantage - Not the best passive for a fight, but I use it because I don't like wasting time travelling through the map. However, it is STILL a good passive for juking away from enemies, or smoke screening into fights to get healing globes. I like speed, this is just my preference.
Steady Aim - The extra 20% damage is OP as long as you stay AWAY from enemies. Remember you are a ranged hero, NOT a close combat specialist. Act like your class and do what you are meant to do.
Archery - Extra damage is always nice.
Technically, to perfect this build you should swap out tactical advantage for "Perfectionist" post level 45 due to the 10% discipline cost reduction. But I don't need it because I destroy anyway.
Notes
Sometimes, it is just unnecessary to smoke screen/vault when you don't have to, especially when you can just left click away from incoming attacks and continue shooting. So save the discipline until you really need it. Of course...zooming across the map with vault and smoke screen is ALWAYS necessary :P
Remember the point of being a Demon Hunter is to deal massive damage and NEVER get touched.
I would also like to add that with Elective mode available for abuse, ABUSE IT TO YOUR LIKING! Remember a build is simply your personal preference of how you play, so use whatever works for you, and enjoy the game!
Juke like a pro, kill like a boss.
Best Answer
So, any Demon Hunter Build is going to divide its skills into two basic categories. Tools You Use To Stay Alive, and Tools You Use To Kill Things. In general, these two categories are largely separable, with the former category being the one that changes radically in Inferno. I'll cover both here for completeness sake, but keep in mind that the latter section allows substantially more flexibility.
Staying Alive
There are two schools of thought for staying alive. The first is built on maximizing Smoke Screen uptime at all costs, through the use of the Lingering Fog rune, Preparation with either Focused Mind or Backup Plan (to taste). Multishot with Suppression Fire, as are the Nightstalker, Perfectionist, and Sharpshooter passive skills. These builds have become somewhat less popular after the most recent round of hot fixes, as the maximum possible uptime has been reduced considerably, but Smoke Screen is still an essential element of most builds, regardless. Since the most recent hot fix, you may also consider replacing it with Shadow Power with the Gloom rune. You'll experience a higher uptime of less damage reduction (-65%, rather than -100%). If you go the Shadow Power route, you'll probably want to focus on offensive skills that provide more health regen (see below for options there).
The other school of thought is to maximize your kiting ability. While Smoke Screen is still essential to most of these builds, they may forego some of the other +Discipline stacking options in favor of abilities like Caltrops and Vault, particularly in combination with the Tumble rune, which makes it near-spammable.
Either way, the key is to select skills that maximize your ability to not be hit. Whether you do this by increasing your invulnerability uptime, or by augmenting your mobility is up to you.
Killing Things
On this front, you have much more flexibility. Elemental Arrow is incredibly popular as a main attack. At a cost of only 10 Hatred, you can almost spam this exclusively in most encounters - Hatred builders aren't often needed, (especially if you use the Bat Companion, see below) which means that you can rely on this skill primarily for damage. The two most popular runes are going to be Frost Arrow, which offers high single target damage, decent AE, and a snare effect, and Nether Tentacles, which offers the best damage on single-target encounters, as well as a decent life-leech effect. Screaming Skull is favored by more kite-centric builds, as the fear effect offers a tremendous amount of crowd control - it's not as reliable as some other options, but it's potency and spammability more than makes up for it.
Rapid Fire is also quite popular, particularly with the High Velocity or Bombardment runes.
Hatred builders, by contrast, are much more to taste.
Evasive Fire is a very popular Hatred builder, but the risk of spending Discipline by vaulting unexpectedly is often enough to make it less useful than the alternatives - especially when action bar slots are scarce after stacking Defensive skills. Additionally, the damage isn't terribly high, and it offers a minimal AoE coverage or additional utility.
Entangling Shot is probably the most popular alternative, as the slow is handy, though the damage is pretty lackluster. Bola Shot and Hungering Arrow have proponents as well. This slot on your bars in particular, is largely going to be to taste.
And Then What?
At this point, you have a Hatred-Spending attack, a Hatred-Generating Attack, and probably 2-3 skills allocated to defense. (Smoke Screen or Shadow Power, and some combination of Prep, Vault and Caltrops). You can fit 1-2 more skills on your bar. What do you take? There are a few major contenders:
Companion, probably with the Bat rune - this is an easy attention-free source of additional damage. More importantly however, by generating 3-hatred per second, it allows you to use Elemental Arrow 5 more times (or get 5 more ticks of Rapid Fire), give or take, before running out of Hatred. That's a Really Big Deal, and a lot of extra damage, before even factoring in the 45% Weapon Damage that the bat does on it's own.
Marked for Death, particularly with the Death Toll rune is popular for Shadow Power and Nether Tentacles based builds for maximizing health regen. It's less useful if you're doing a lot of kiting, or concerned with AE damage. It's also very potent in combination with Nether Tentacles -- especially in 'true' single target (i.e. only one thing on the screen to hit) situations.
Multishot with Suppression Fire, as mentioned above, is a popular option for maximizing Discipline Regen. Alternately, with the Fire At Will rune, it becomes a popular AE option for builds that are more focused on single target damage with other skill choices (i.e. (Rapid Fire)
Spike Trap, particularly with the Scatter rune is popular for kite-centric builds - dropping one at a tight choke point can be devastating.
Passives
The only really important one here is Archery, which, in combination with a 2H Bow or Crossbow, is a massive increase in damage. If you're stuck using a Hand Crossbow, this is less important, but you should really be trying to get your hands on a two handed ranged weapon as soon as possible in order to use this passive. It provides an absolutely staggering amount of additional DPS.
Beyond that, it's largely to taste. If you're focused on SS/SP uptime, you'll want some combination of Night Stalker (possibly with Sharpshooter to support it), Perfectionist, and Vengeance. A kiting focused build may want Cull the Weak or Tactical Advantage. You have a lot of flexibility here.