*Menu Tip* For most of the time, if a dialogue box has two buttons to press, the left hand button is 'cancel', and the right hand button is 'accept'.
This is true for buying items, writing letters and adding and removing tickets to the map. If in doubt, press the left hand button.
The interface, from top-left anti-clockwise, to top-right

Your current location - Japanese addresses read the opposite way round to Western addresses, so the largest area is on the left, smallest on right.
The first three kanji in this example simply say Tokyo so are unimportant as the whole game is in Tokyo.
If you want to visit a specific location, the kanji after Tokyo are the ones to match up to maps, train tickets or locations mentioned on the internet. (this example is Shinjuku)

Group - the members of your group/party
Map toggle on/off
(unknown - currently non-functioning)
Place names on/off (on map)
Center on self
Map zoom
+ zoom in
- zoom out
Slider can also be used as well as the mousewheel
Chat window
Actions/emotes
(unknown)
Open chat bubble
The mini-map
Current location address
The light blue icons are train stations
The green buses are bus stops
Famous / Interesting landmarks appear as a small icon representing them.
The orange arrow is yourself
Green arrows are to scroll the map - smooth scrolling is possible by left-clicking anywhere on the map, holding the button and moving the mouse.
Chat window
Icons from left to right:
Own messages (only you see these)
Chat
Whisper / PM / secret messages
Actions