He's a handful, all right. He keeps you up at night; he's always missing the facilities. And he goes nuts when a man in uniform approaches the door. But your pet partner - whether a dog, a cat or a hamster - need not drive you crazy. Try the practical tips to train your four-legged family members. After all, who else greets you at the door, running around in circles and giving you little love sniff-sniffs? Real Simple asked readers to share their biggest pet hassles at www.realsimple.com, then consulted experts for their solutions. Here are the results.