Do Bitcoins mined in a pool automatically transfer to your wallet? I've installed the GUIMiner app and the Multibit app.  I am in a mining pool, and I have about 17 shares thus far. Do the Bitcoins transfer to my MultBit wallet automatically or do I need to do it manually?
Generally, no.  Usually you have to specify the address in your wallet and the threshold minimum so the pool sends your funds. 

Most pools require some kind of registration; Eligius.St only requires your wallet's payment address.