In order to find the Thieves Den you need to get a map from no other than a thief himself - my advice is to go fight them at Rocky Path!
As for the Alchemy Contest place you'll find the map at the Refuge (that little shop and inn sort of house near the eastern exit of Rocky Path) - just check some scrolls there!
The temple in Green Grass needs an item you find at the Monastery in the Rocky Path - search the upper floor!
Old Tibor needs some special wine, search the wine shelves at Sapphire Caves underground area!
Happy hunting!
