The planet is an Earth-like planet... however, it is tidally locked to the sun-star. This means that one side of the planet ALWAYS faces the sun, and the other ALWAYS faces away from it. Normally, this would mean bad things, as one side would be super hot and one side deathly cold. If the planet had an atmosphere, it would be in constant hurricanes, as the heat and cold exchange sides - HOWEVER, if the planet was mostly water-covered, this heat exchange could be facilitated by the water. One side of the planet would be ever daylight and SUPER hot, and the other side would be ever night and really cold - but with the water currents, it should temper both of these halves, meaning you could actually make them habitable. However, the water would be a MESS - since it would be in constant motion, you would get powerful currents as the water migrates, not to mention the tide from the moon.

Now, you don't want it to be really cold (I'm talking subzero, arctic conditions or worse) and you want to avoid sunlight, which means the hot side is off-limits. Imagine a band around the planet, a belt right around the middle between the hot side and the cool side. Expand that belt a bit so that it's 40 degrees wide, 20 degrees on each side of the belt (I'm fudging the numbers here). Now, drop Australia onto the edge of the band facing the cold half of the planet (that's all the land you get, too much land and you get hurricanes). This continent would live in darkness, not QUITE night, but not QUITE dusk either. As people walk from one side to the other, they would notice a light difference (It would get slightly lighter the more you approach the centre of the band). What I would do is either put your rich, upperclassmen here, or stretch the continent a bit so that this light change is negligible (You now have a sausage the size of Australia in the middle of the ocean).

I would smack a mountain range somewhere on this island (Not sure why, perhaps volcanic). This would give you more consistent rainfall.

This "temperate" zone on the continent (where your people live) would be cool and constant in climate. You can do whatever you want here, though it would be quite windy (Not gale force, just windy). The lower temperature limit would probably be -20 C, and the upper limit would probably be 15 C (Remember, this is constant and never changes by more than a few degrees. There are no seasons). Personally, I'd go with the upper limit. You'd have to dress warmly, but not bundle up. People could comfortably wear lighter clothing and heavier clothing, so the average person would wear clothing of light sweater consistency.

Because of the water storms, one side of the continent would be subject to constant tsunamis, which would cause insane amounts of erosion (Big, jagged cliffs with deadly sea at the bottom, maybe?) This means that the continent would be shrinking, I guess, but it isn't a big deal for your story (It would take a LONG time). The other side of the continent would have more peaceful, calm sea to a point- anyone going out with a ship would soon encounter gale-force water storms and die. This confines people to the continent, preventing them from ever seeing the sun.

The moon is just a moon, rotating around like Earth's moon does. I personally would make the moon rotate a bit faster than Earth's moon, say 10 days (so a "day" on the planet would be 10 days, one Moon phase).

Plant life would be very limited, as there isn't enough light to properly photosynthesize... however, there are forests in your story. Here's how I would do it.

The trees are VERY thick and VERY large, with deep, deep roots, and the crust is thinner than on earth. This means the deep roots get to be... GEOTHERMAL! No photosynthesis, no leaves, but very deep roots. Geothermal wells on Earth can be very shallow or very deep depending on many factors. Here, I'd give the trees a root depth of around 2 metres for a young sapling, and 7-10 for a big, old guy.

Fruit from the trees (containing seeds) would probably be large and very, VERY sugary. This is because the tree sapling needs to have enough energy to grow to a point where its roots can start absorbing geothermal energy (and the fruit would be its only source of energy until it starts the geothermal process). The fruit (say it's one foot in diameter) could have a big pip in the centre. When the fruit drops to the ground, the pip starts to grow into a... tree fetus? This "tree fetus" would extend one very long root (like a thin tentacle) into the ground, absorbing the rotting, sugary fruit for energy. If it gets deep enough to start a geothermal loop, it survives. Otherwise, it dies. Once it gets one root down there, it slowly grows other roots before growing a large trunk and branches.

Since the seeds NEED the fruit to survive, the seeds cannot be planted without the whole fruit. This means the fruit cannot be eaten and pooped out somewhere else by an animal like fruit on Earth is - the "tree fetus" seed will only grow if it naturally falls from the tree. This means the trees would be very close together and VERY tangled up, leading to a very spooky forest setting.

You would also have carnivorous "plants" - creatures that are stationary and have roots, but they eat animals. Geothermal isn't needed here, their energy is from MEAT.

You could also have a lot of fungi, or fungi analogues, growing off rotting trees.

At the top of the tree canopy, you could have REAL plants that live off photosynthesis, but they would be tiny (Perhaps a delicacy).

To prevent the forests from reaching across the entire continent, natural wildfires would be common to thin the ranks of the trees (much like what happens in Earth forests). Wildfires would be caused by lightning from storms.

Most of these tree species would exchange genetic material with flowers pollinated by small creatures (insects or whatever, like bees). They would be extremely pungent to make up for colour (colour is useless without light), so the forest would smell of flower smell all the time (however you want that to smell. It can be beautiful or disgusting).

Now, the Lux trees have something special. Instead of using flowers to pollinate and fruit to grow a new tree, they combined them into one. The fruit contains genetic material spread throughout it, and can absorb genetic material from the juices of other Lux trees (brought by the mouthparts of feeding animals). The fruit also contains the pip to create a new Lux tree. Now, getting rid of the flowers meant also getting rid of scent. To attract animals, the Lux trees evolved so that their fruit luminesces. This glow attracts animals to the fruit to eat and exchange genetic material with other trees. When a Lux tree accumulates enough diverse genetic material, some of its fruit ceases to glow, and then they fall and rot like the other fruit does. Lux trees can take as much time as you want for them to grow (Bigger fruit, faster growing. You could even make them really large, a metre in diameter or so).

You can have fungi with bioluminescense. You could even have people wall their houses with living fungi to light their house. It would not be as bright as Lux trees or a candle, but it would be mildly effective.
If you wanted to grow any plant other than a tree (which has the fruit to sustain itself), you would NEED to bring dirt from the forest. The dirt would be rich with composted creatures and plants, so things like fungi could grow in it.

Humans would have to have evolved to live without sunlight. If you wanted to be picky, you could have a special fruit high in vitamin D that people would need to eat to survive.