The first way is to have the player get their coordinates by holding Ctrl-Alt-Shift-L, have them copy the coordinates/command, then paste it in chat. You put the coordinates/command into the console and you will be teleported to them.
But what if you can't get the coordinates from them? Not every player will be eager to have an admin check out what they're doing.
The second way to teleport to a player is to open the console and type "ViewPlayer PlayersName", Then in console type "Teleport", Next you'll type "ViewPlayer YourOwnName".
It's the only solution I've found that lets you teleport to a player without their direct cooperation.
Let me know if you have any questions, or know any other ways to teleport to players.
And if you're not a server admin but looking for a good server to play on try searching for Keangdom in the server browser. We'd love some more people to play with.
EDIT: We've noticed the second method only seems to work if Steam names are used. If their in-game name is different than their Steam name, you still need to use their Steam name to teleport to them. I'm not sure what the best way to find their Steam name is.
EDIT 2: You can get a players Steam username by typing in the console "PrintPlayerInfo PlayersInGameName" *Note: Make sure you push ~ twice to open the full console, otherwise you won't see the results.