Use MyCheats . com - there is a full video walkthrough.
Death Mountain
After you complete the Forest Temple the twilight is no longer in that region and Link must travel to the next region of Hyrule to rid it of the twilight
It's on the map.
beat the boss
the forest temple
get the boomerang.
The big key
You finish off the forest temple mini boss
In Twilight Princess, the only monkey whose name is given is the forest temple boss monkey - his name is Ook.
as soon as you defeat the Minny Boss in the Forest Temple you get the boomerang
collect all the monkeys then defeat the flower boss
In the Forest Temple, the very first one. If you want to know exactly where they are in the temple, walkthroughs are very helpful.