Thanks guys for answering! We've tried commanding "sit" (still working on "stay") but it's tough for him to concentrate/obey when he's all excited and happy like that. Friends of ours have recommended a light squirt of water from a spray bottle when we catch him "in the act" (play-biting our toes, trying to chew our flip-flops, etc.). They claim it works really well. But I certainly don't want a fearful dog...(heck, it's hard enough for me to yell at him! I feel so guilty afterwards! But he needs to know what is unacceptable behavior, now.)