Valid teleport destinations include towns, dungeons and other players. Most destinations require a teleportation license to be active, except for town travel which can be conducted at any travel agency in exchange for gold and will.
Any town previously visited can be moved to by selecting the desired destination from the town tab in the journal. Similarly, any floor of any dungeon can be moved to using the field tab in the journal. Any player that is registered as either a friend, party member or guild member can be moved to using the actions menu in a whisper window with the player.
Tip: When you are using the automatic teleportation license that all players get from Main Character ~level 12 until level 80, you can teleport to towns you haven't previously visited and they will then be on your visited list, so that you can teleport to them later using the Travel Agency or Teleportation License. So, if you take advantage of this to visit all towns before you hit level 81, you won't have to walk/run to all of those towns to discover them.
Teleporting initially requires 80% of a players will, but scales with the level of the hero. From level 20 onward, will required decreases by 1% each level until level 80. Thereafter, teleporting only requires 20% will.