I think its like a 10% chance of getting any of the rusty weapons.
you do a gobal mishin
Firstly it is NH3 not MH3 and it does not have any oxygen atoms dumbster
kill the king
mine in expert volcano quests
In the sandy plains area 6 I think.
Rare trade with the trader in the village offline
i regret to say but MH3 is only released on the Wii
After you do accidental investigation (hunt a gobul), then talk to the argosy captain(make sure he went to the hunters realm, then go talk to the wyverian artisan and he'll say he the argosy captain told him how to make long swords. the first weapon you can make is the ananta boneblade. later after you kill lagiacrus you can make thunderclap and so on etc.
There are two ways. Wait for the Jhen Mohran quest online then mine on it's back OR... Get to the Tundra/Volcano and then mine in numbers 7 and 5 (Tundra) or 9 and 10 (Volcano)
There are no golden nuggets in mh3, but there is wyverngold and the different eggs. You get wyverngold by killing high level monsters in the deserted island offline. You can get eggs by sending the boats to the treasure areas.
the upcoming God Eater is highly anticipated as it another MH type game. also MH3 on PSP will be release in Japan near the end of the 2010. Hope the US and Europe release comes next.
There really isn't a best sword in mh3. It all depends on what you want it to do. I suggest making a set of sword and shields, 1 with each element. Equip each one depending on your targets weakness. E.g. Qurepeco has an ice element weakness.