Wheelbarrows: You do not need wheelbarrows to make stockpiles work. Wheelbarrows are useful for hauling heavy things like stones and hauling many things at once, but there is no particular reason you need to haul ammo via wheelbarrow.
The number of wheelbarrows you assign to a stockpile is the limit on how many dwarves can be assigned to haul things to that stockpile. Assign just one or two if something is low-priority, like if you don't want too many dwarves out and hauling wood from the surface inside at once.
Atom Smashing: It gets its name from the fact that
nothing at all remains when you do it. You want to set it up so that there is nowhere the creature can go when you flip the lever. If you have a long bridge, you want it to come down on the creature, but you can also simply put where the bridge is raised directly against a wall, and they will be squished between the raising bridge and the wall, then, as well. In my first fort, I also had double-drawbridges at my entrance as a "clapper" that raised into one another to squish goblins. (Although some would be lobbed diagonally and miss the squishing, but fall into the alligator pits the bridge spanned... hehehehe.)
Quantum Stockpiles: The easiest way to use them is by using minecarts as they are intended for use. Make them, they make fortresses SO MUCH EASIER. If you have stockpiles that get full because you are making so much crap, DO NOT just dig out more space to stuff more things in the stockpile. On that path lies only pointlessly long treks through giant stockpile wastelands. Either throttle production (idle dwarves are not a bad thing), or set up a simple 2-tile rail track with a track stop and a 1-tile stockpile the track stop dumps into. You can stuff any arbitrary amount of material into a single tile.
Quantum stockpiles also significantly reduce your FPS drain due to pathfinding, to the point where it can double or triple your FPS if you have hundreds of thousands of items, and pathfinding is your largest FPS bottleneck.
Magma Forges: Simple magma forges can be run deep within the earth. It's a major traffic snarl to have to march down 80 flights of stairs to get to work and back, but you can set up a temporary dining hall, food stockpile, and residential quarters to keep the actual metalworkers down there full-time while haulers bear the brunt of the trek while you set up more permanent solutions to the magma distance problem.
First, find your magma. You'll probably find it easiest to just open up the lowest caverns, and look for a large block of obsidian that reads as "warm stone" (flashes a yellow * on red background) in the (d)esignation menu. This is a magma pipe. It might stretch several floors above the lowest cavern, dig an up/down stair down from above along the outside edge of where you saw the ring of obsidian until you start seeing some obsidian.
From one z-level above the edge of the obsidian, set up a
magma-safe pump whose "draw from" direction is over the magma pipe. Put a door next to the impassible (output side) side of the pump - doors block magma, just remember to lock it to keep stupid dwarves from trying to open the door to enter the magma stream when you're ready to pump. Then dig out a trench for where you want to have magma forges powered.
One floor above, make the space where you want to build your magma forges. Smelters and kilns have an impassible space in the center-North tile, while magma forges have impassible tiles in the center-East and center-West. So plan out where you want to put those forges, and make sure that the space beneath the impassible tiles has access to magma by digging out the floor beneath that point. You should probably set up at least two or three smelters and two or three forges. You might want a couple kilns or glassmakers, as well, if you have glass or fire clay, and are otherwise poor in good resources. It's a pain to make more, and easy to leave an extra workshop doing nothing, so make an extra.
If you want to be safe, build something to drain the magma out. For water, I just use a hatch to an atom-smasher as my drain, but magma usually needs to be pumped out, so you'll need to build another magma-safe pump into a magma-safe atom-smasher to eliminate the magma if you want to eliminate the magma. I mention it because I consider it good practice to always have a safety kill switch, but you can skip this for simplicity's sake for now.
When you've excavated it all, make sure everyone is out, give the haulers some time to clear away the boulders, (or just forbid the boulders, and hide them), and lock the door to the magma trench when everyone is out. (Alternately, you can skip the door, and just plain build a wall, which may be safer.) Remember, magma can flow diagonally, so don't let there be any spot where magma can leak.
Next, channel out the path to the magma pipe to expose the magma. Then, place a magma-safe grate on top of the tile you channeled to keep magma crabs from killing your dwarves.
Now, you are ready to pump magma. This is a simple design, so just pump magma manually. Yes, they'll be fine.
When the magma fills the trench, turn off pumping, and channel the tiles you marked for the impassible tiles on the magma smelters and such, and then build your magma workshops on top of those designated areas.
This setup may look a little complicated in text, but it's really not. I've set up magma facilities like this
in the first Spring, so it takes nearly no effort at all. I use this to get metal going early in dangerous embarks where I can't postpone metalworking until I get magma up to the surface.
Moving Magma: It takes considerably more work to get magma to the surface.
Pump stacks are relatively simple by concept, but a massive undertaking in time and labor in practice.
The wiki covers it. Pump stacks are the best (and possibly only) way to handle large-scale applications of magma, such as magma flooding traps, but may be too much effort for just getting a magma forge running. They also murder FPS while operational.
Magma pistons are something of a more "advanced course" but can easily provide enough magma for a few forges fairly early on. It relies upon exploiting a quirk in cave-in mechanics that makes fluids teleport from the bottom to on top of a wall that is crashing down on top of the pool the magma was in. This is good for getting small amounts of magma to the surface fairly early in a fortress, so it's good for early forts, but it's also complex conceptually, so you should spend some time working with deliberate cave-ins in a practice fort before you try it "for real".
Magma Minecart tracks are a third option.
Here is a design, but there are several, including
on the wiki. Larix also has
a great design that works very efficiently. These are simpler, faster, and less FPS-murdering than pump stacks, are less confusing than magma pistons, and provide a middle-ground for how much magma it can provide. You can't flood the world, but you can easily feed any relatively magma-conserving project.
Miasma: Miasma is generated by rotting dead creatures (not vermin) or creature body parts.
Miasma generates a "cloud" that looks similar to sand tiles in the default tilesets. (It is hardcoded, so no tileset can change what it looks like.) It also obscures
everything else in a tile, so you can't mistake it when you see it. If you don't know where it's coming from, try looking further up or down in the fortress.
Also, miasma thoughts can persist for a long time (a whole season), so it may be that whatever was rotting has been eliminated already.
The easiest way to handle this is to set up a refuse stockpile outside (no miasma is generated outside), and let dwarves dump stuff out there.
A slightly more complex, but better way of handling refuse long-term is to create a garbage dump activity zone next to a channel. They will toss anything marked with "D"umping to be tossed into the channel. Make the channel several z-levels deep, and at the bottom, set up a small drawbridge within an entirely enclosed space to be an atom-smasher. Every few months, pull the lever a couple times to operate the "garbage compactor".
If dwarves are not dumping things, it is because you have no free haulers. Shame on you. Turn off some other labors and take some workers off of making things to clean up your fort before you make more junk that ALSO has to be hauled. Remember: Idlers are a good thing.
Control Rooms: Control rooms are rooms where every lever in the fortress designed to be used more than once is set up. Either operate it with a vampire that is locked in, or use a noble who you can lock into their room. If a noble, give them food and booze. Make one lever control a drawbridge that forces that room closed so NOTHING gets in.
If it's not a vampire, you might want two dwarves just in case one goes on break (noble consort dwarf, possibly). Make two levers, each with a profile such that only those dwarves that are dedicated lever-pullers can pull them that aren't connected to anything, and set that lever to be pulled, "DO IT NOW!", to get the pullers in the room. With the airlock shut, they are ready to follow any lever-pulling commands with no distractions.
This forces a dwarf to have nothing better to do but pull levers.
Set up stockpiles to put food and drink and possibly also a pick for a total doomsday scenario, as well as beds (not a problem if this is the baron's bedroom, anyway) to keep the pullers happy and fed. Vampires don't need these luxuries, but making it their bedroom or study and having nice furniture will keep them happy enough admiring their own chairs.
In the worst-case scenario, this is also a fallout shelter that can outlive the destruction of the rest of your fortress.
I will also put up some design tips, but this post is already monstrously long as it is, so I'm getting bored