In case anyone is new to multimining, I recommend using an exchange like Cryptsy which has auto-trading.

Put your Cryptsy deposit address for each alt-coin (eg. PPC, TRC etc) in as the multipool.us withdrawal address, and on Cryptsy set the coins to auto-sell. This way you'll still just get BTC from your mining, but a little bit more when the alts are more profitable to mine.