To get little bonus items out of Friends of Mineral Town, you'll need to hook the game up with A Wonderful Life for Gamecube. When the two games connect, information is passed between them and changes a few things in both games.
To connect, you'll need...
Gameboy Advance console
Gamecube console, controller, and memory card
Gameboy/Gamecube Link Cable
A copy of Friends of Mineral Town
A copy of A Wonderful Life
To begin, start both games up (of course) and then in Mineral Town head to the Goddess' Pond on Mother's Hill. You'll have to bring something to throw in the pond to make her appear. When she asks if you would like to connect, select Yes and then stop and wait at the next prompt.
In A Wonderful Life, run to the eastern side of the map and start heading up the mountain path. Nik, Nack, and Flack will stop you from running up the hill and say you can't go any further unless you want to connect to Friends of Mineral Town. Tell them you want to connect and then after reading their instructions, they will ask to confirm the connection.
At that point I find it easist if you select Yes in FoMT, and then select Yes in AWL. The two games will make some cute little chiming noises and your tv screen will turn white. The game also auto-saves while transfering.
After you connect your two games together, the process is finished. You can turn off your Gameboy if you want to, although I always save again just in case *grin*. You'll still have to play through FoMT in order to trigger new items to be sent over to AWL.