You can spawn them by downloading it off websites. But I would not do that, because most of the data in the spawn commands and such are viruses. So, it seems the easy way to do it at first, but it also can be very harmful for your computer.
During the day, away from spawn (about 1/3 of map), on grass
Yes, it can rain in Terraria. Special rain-themed enemies may spawn during this time, like Umbrella Slime and Raincoat Zombies.
You never actually 'sleep', all beds are for is to change your spawn point.
the eye of cthulu will spawn at night rarely and goblin armies will attack
Harpies only appear if your altitude is high enough. A sky island works nicely.
First, you need bukkit. Install the Essentials Spawn plugin and type "/setspawn" in the server to set the spawn.
yes if they set spawn in the nether, but not many do
Terraria happened in 2011.
I believe because when a spawn is set, the x, y, and z coordinates are saved but the Pitch and Yaw, (Head position), is not saved.
Search "Terraria invedit" on youtube.
Just Google Terraria servers and copy the ip address into the multiplayer slot on terraria.
Because that where the terraingen system set it up for you to spawn, it's 100% random as far as I know.