Nonsense to they naysayers!
I heartily recommend constructed walls. Mixing concrete is (relatively) cheap and is an effective way to build walls to deal with real world problems.
Beware of digging too deep! There's nothing wrong with the first z-level. Worse than demons, the deep holds polluted aquifers, impenetrable layers, and the risk of cave-ins and floods.
Doors on the ceiling have annoying properties. Either they open down, and have a tendency to allow water in, or they open up. What happens when you live underground without electricity, hermit-style, while your food stockpiles lie above, and a tree falls on your door? You're hunting for vermin.
Z-1 with a door in a cliff-face is recommended. If it opens inward, you can escape natural disasters, while still protecting against water flow.
Ventilation is important. A U-shaped tube in your ceiling allows gas to pass while preventing flooding.
Much as in DF, the best place for "refuse" stockpiles is outside of your main fort. You will probably be able to maintain adequate ventilation for oxygenation, but not adequate for fume dispersal. While real-life humans can develop a high tolerance to miasma, what happens when you have to entertain a foreign liason?
Flooding is a very real problem in real-life DF. Water levels rise and fall. ALL building materials are permeable to water to a certain extent. You will need a system to drain your fort that can be used in times of need, while preventing the upflow of water. Experimentation in your own biome is important. I would recommend building with the least permeable materials you can find, and designating a lower flood-level that is sealed from the main living area. Unlike dwarves, you will find yourself using water for the purposes of hygeine and hydration. You should consider water a refuse material, and locate water stockpiles far from your main fort.
Real life magma is very dangerous to work with, and you may have trouble locating a caldera. Luckily, metal materials are easily available as a trade good. However, it will occasionally get cold. You will, on occasion, desire heat, typically when your floodgates fail. Do not, under any circumstances, attempt to place any flaming goods in your stockpiles. Do not place any flaming goods underground, or you may suffer very unhappy thoughts.
Cave-ins are relatively rare on upper Z-levels when working with constructed walls. As with DF, do not allow any unsupported areas, or they will cave in. In real life, however, constructed structures tend to shift. A broad base of support will minimize shifts. Build a floor with more surface area than your living area.
Conversely to dwarfs, humans tend to suffer from surface adaptation. It is irreversible; it is probably too late for you, as a walking talking Homo sapiens, to prevent surface adaptation. Life without the sun is unrecommended. If you choose to live without the sun, you will find your bones weakening, and will probably suffer very strong unhappy thoughts. This can be mitigated with Vitamin D supplements and lots of friends. A pet is a good idea, but be aware that most pets suffer equally from surface adaptation.
In the seed I am familiar with, goblin and kobold civilizations are rare, as are megabeasts, and you are unlikely to experience problems with the above. However, not all humans are friendly, even if you never seize any trade goods. Ranged steel weapons are ridiculously overpowered, but very difficult to manufacture yourself, because of the bugs with magma. However, ranged weapons are readily available as trade goods with most civilizations. With a season of hauling tasks, you should be able to afford a weapon and ammunition, and even a novice is deadly. Armor, in real life, is pretty much worthless. Since you will suffer unhappy thoughts from sleeping with your weapon, you will want to rely most heavily on forbidding your doors during vulnerable times. Very few humans are building destroyers.
And whatever else you do, remember that you probably won't get it right on the first try. Don't worry! Losing is fun! Soon you'll be booze-bombing nobles like the best of the survivalist recluses!