The only real requirement is that the sukkah be big enough to sit in and that it be roofs with an organic material - wood, branches, bamboo, reeds - that is just solid enough to provide shade, but not solid enough to keep rain out. It's a temporary thing.
Practically, it should be big enough for a tall man to stand in, and large enough to hold at least the family around a table and chairs, because all meals will be eaten there. One can put down a rug, or put up a handwashing sink attached to a garden hose. They can be decorated - families with kids let them make them; others buy them. I've seen paper chains, stretchy metallic things, accordion pleated fruits and veggies, plastic fruits and veggies, *real* fruits and veggies, pepper lights. Gotta have lights, so you can eat dinner. I've also seen pictures of famous rabbis. We don't have kids, so no homemade ones, and we don't do the rabbi's picture thing.
So, what sort of a hut did we get? We got something called the "Ease Lock." It's a metal framework that fits together without tools and is stable enough so it doesn't need to be tied down, with a tent that wraps around it. This tent is fastened top and bottom with Velcro, and comes with clear patches for windows and a door thhat can be zipped closed, opened all the way, or closed with a zippered screen. It comes with a "roof" made of a loosely woven bamboo mat, and some boards to support the mat. We will use twine to tie it down. It's 6x8, large enough to comfortably hold a resin table and four folding chairs, which we have to buy. It also came with decorations. We have to get a friend with a truck to get it to us.
We could have spent a bit more money and gotten one made of fiberglass panels, but we don't have the storage space. This one stores easily. All we'd have to do is make sure the tent part is dry. We're also taking advantage of this to invite some friends from our synagogue. She's wheelchair bound and would have to be carried up our stairs. The wheelchair still wouldn't make it through the door opening, but it's much easier to carry her to a chair.
I'm rather excited. We haven't had this opportunity before. Finally, we can eat all our meals at home in the sukkah.