I'll just copy and paste from the Main WoW Forum FAQ for you.
Quote:
11. I see coordinates show up on some posts. How do I get coordinates to display in my game?
The stock game does not display map coordiantes. You need to use an add-on in order to display them. Many different coordinate addons can be found at curse-gaming:
Punky Coords
Koordinator
cMinimapCoordinates
MetaMap
SimpleMinimap
Alpha Map
Additionally many full-blown interfaces like Titan Panel, have the feature built in.
or, you can create a macro:
Create a macro using this script (just copy & paste it):
/script px,py=GetPlayerMapPosition("player")
/script DEFAULT_CHAT_FRAME:AddMessage(format("[ %s ] %i , %i",GetZoneText(),px*100,py*100));
You click on the macro and it will give you your coordinates in the chat pane.
Now you can use all those quest tips where they only give you coordinates for the mob/item you are looking for.