Here is build I have had a great deal of fun playing throughout Normal and Nightmare.
Build: http://us.battle.net/d3/en/calculator/demon-hunter#aSYTki!Yce!ZZZaaZ
Demon Hunter is about kiting and killing stuff at a distance, and this build has all of those elements necessary to pull it off well. In the build are the tools you need to DPS on the move and keep stuff at range.
Hungering arrow with the Cinder Arrow rune is a great boss killer and useful for seeking out foes through doorways and down poorly lit tunnels. It will turn once and has a chance to pierce foes. I like the Cinder Arrow rune because usually I am using this not to clear groups of foes, but instead to bring down strong singles and this rune maximizes its damage on the first hit.
When facing bosses like Diablo, you can run off until the boss is offscreen and confidently fire these back in the general direction where you think he is and chip him down steadily. It is also possible to hang up an enemy on ground clutter and use this arrow to fire at right angles around the obstruction. If you walk along your screen diagonal you can see stuff before it wakes up, and use this arrow to kill it before it knows where to run and kill you. If you ever play with a group or a Witch Doctor in which it is hard to tell friend from foe, you can always chunk hungering arrows (or strafe) and hit targets.
Elemental arrow with the Frost Arrow rune is your main tool for dealing with packs and tight clusters. Your goal as a DH is to cluster your foes as tightly as possible so as to maximize the mulit-hit of this arrow. Frost provides the slowing which buys you time to retreat.
The best tool for generating clusters is Caltrops with the Torturous Ground rune. Laying down Caltrops in a choke point (doorway, at a corner) causes anything chasing you to slow in the Caltrops. I tried the Hooked Spines rune (ups slowing to 80%) but it is not as effective as Torturous Ground which roots them for 2s. A pack of enemies that is strung out in a line will hit the caltrops. Lead members get rooted and trailing members catch up, clustering tightly in the trap. Playing your DH well involves you always eyeing the field and thinking of where best to lay your Caltrops and when to retreat.
Build continued after the page break..
I like the Spider Companion because (a) it is indestructable, and (b) it slows your target. This is very useful against leapers and porters who bypass caltrops, since the spider seeks them out and slows them. If you have an open field with few choke points and you face a difficult foe that is not going to path predictably, the spider gives you a chance to slow your target.
Strafe with Drifting Shadow (for full speed while strafing) is a skill I see in few guides, and I really do not understand why. First off, nothing beats strafe for busting barrels and destroying stuff. Just tap this every 2s or so and you will leave every single barrel broken as you go down the road. More importantly, this is one of the few skills you can use that lets you maintain full speed and dish out damage. While one can tap the shift key and pump out a hungering arrow that will do a U-turn and home in on things chasing you, that time to fire it puts you at a standstill and things catch up. Strafe can be freely hit as you move to do damage to whatever is chasing you without slowing down. The final great use for strafe is when you face enemies that are widely scattered, or flee...most of the other arrows are meant to fire at clusters, but Strafe will hit whatever you face in a 360deg arc.
Sentry with the Spitfire Turret rune gives you a set and forget DPS source plunking away at whatever is chasing you. One tactic I like verses mortar users is to set a sentry down, then circle the sentry while strafing. Because you are always moving, every mortar they send off lands where you used to be. The combo of strafe and sentry will grind down that pack to a more managable number. Many bosses in this game will close on you, then go through a animation before striking you. If you are always on the move, these blows do not land. Sentry also works nicely if you lay down caltrops, then put sentry on the far side as you kite beyond the caltrops. The sentry just plunks away at whatever slows in the trap for more DPS.
Passives
For passives I like Steady Aim (10yards is very short, look at a chart of distance sometime) because that 20% damage boost is up a lot. Cull the weak leverages the slow from caltrops/frost arrow/spider for 15% more damage. Archery is just more DPS increase.
A basic technique you must master is to establish a line of retreat into which you can kite, and usually this is along your clear line. It is usually best to clear around the edges of a map to avoid adds coming in from both sides and bypassing your caltrops. When you perimeter clear, it is easy to identify your safe line of retreat because it follows the map edge.
Sometimes you get door-jumped in a mini-dungeon. This is where you zone in and are immediately swarmed. The way out of this mess is to run forward into the unexplored dungeon until you can find a choke point to dump a caltrops on and force the entire zerg howling for your blood to get stuck in that caltrop trap. Even if you die doing this, it is preferrable than having that pack stacked up at the zone in point for the instance, damaging you before you even completely load.
Gearing for this build is simple as you need not really focus upon vitality or defensive attributes. Your primary defense is not getting hit because you are always just a bit out of range. You can therefore load up on gold find or magic find gear, or just go absurd with Dex and DPS attributes to up your kill rate. I tend to search for experience/dex gear in armor slots, and go for leech/sockets/reduced level requirement for the main weapon.
I do not fully understand the tradeoffs between dual wielding and big 2 handers, but my understanding is that giant DPS number you see next to new weapons is what you realize when you click and hold fire a single skill. Slow weapons will have a lower fire rate but hit harder. Fast weapons hit lighter but fire faster. For this build I like big 2h crossbows/bows because frequently what you do is fire, move, fire, move. If the time it takes you to move is longer than the interval between shots were you to stand and autofire that nonstop, then you will lose dps on higher fire rate weapons. If you have a single shot, you want it to count.
Wallers and trappers are your bane. If you get a whiff of one, your immediate goal is to drop caltrops and get that guy off screen. Once it is off screen you can plunk with hungering or guess and fire a few frozen arrows in its direction, but at least at that distance you will not find yourself in a wall, or if you are walled/trapped, it takes longer for them to reach you and you have a chance of it wearing off before they arrive.
Another problem class are the guys that yank you to their position. If you are facing this, just strafe as you continually move. Never stop to fire anything. That way if you get grabbed you continue your movement away from it before it can whack you.
Not all directions are equal for fleeing. If you flee along a screen diagonal, you can see at a longer range than if you flee along a screen edge as your viewing distance is maximized along the diagonal.
Good luck and happy hunting!
