If you're one of those responsible-type parents who promised the kids a puppy last Christmas but took the experts' advice to wait until spring to actually get it, you were smarter than you thought. That's because dog expert Mordecai Siegal has come along this spring with a new book designed to take at least some of the guesswork out of selecting, housebreaking and training a dog to be not only a good pet, but a member of the family.

"This book was a very important, personal statement for me," says New Yorker Siegal, 50, a dog owner for many years and a parent for the last 10. "As the father of three, I know what the problems are in selecting a family dog and they're very special."

Although the book, A Dog for the Kids (Little, Brown, $15.95) contains an extensive section on how to choose a breed of dog that will be good with children, Siegal says it was really designed as a guide for parents to learn more about the bond that children can develop with dogs.

"I wanted to emphasize the value of the relationship between a child and a dog," says Siegal. "Everyone needs a friend who loves them without qualification, and a dog can frequently cut through things that some of us parents can't. That's a direct connection of pure emotion that we don't get enough of."

As an example, Siegal remembers an incident a few years ago when his oldest son was rejected by a group of boys at school that he refers to as "the gang of six. He was really miserable, and I tried to get him to talk about it, but he wouldn't. Then his old pal Pete (an aging Siberian husky who has since died) came over and sat in his lap and made him feel like a million bucks."

And unqualified love isn't all a dog can provide. It can also spell success. A recent survey of Fortune 500 executives, conducted by the Pets Are Wonderful Council, found that more than 94 percent had grown up with some sort of pet in the family.

Dogs can also be valuable companions for children in other than traditional families.

"For the only child, a dog can help flesh out the feeling of family," says Siegal, teaching the child such important social interaction techniques as leadership, sharing and responsibility. Likewise, a dog can help both the parent and the children in single-parent families: parents by assuming some of the emotional burden normally shared by a spouse, and children by providing an additional source of security, love and comfort.

There are, however, wrong reasons for getting a dog for the family.

"The biggest mistake single parents make," says Siegal, "is to get a dog as a substitute human being. A dog must remain a dog; it can't be a parent or a child's big brother."

Another common mistake, says Siegal, is overemphasizing the dog's role to the exclusion of other human beings. "We can all benefit from having a dog, but we need other people, too. There are many other things that should be as important in the child's life as the dog."

Choosing the "right" dog? "It's really not all that hard," Siegal insists. "You just have to do your homework, go to a reputable breeder and get good advice."

"Common sense," he writes in the book, "won't necessarily help you."

As a start, Siegal (whose previous dog-selection book, Good Dog, Bad Dog, is considered a classic) provides thumbnail sketches of 45 recognized breeds that love children. In addition to providing the usual information such as cost, size and grooming requirements, he includes such critical information as ease of housebreaking ("I've found that, after going through diapers, parents are very interested in this"), personality and esthetic qualities.

"My criterion for selecting which dogs to include was which breeds were 100 percent guaranteed to at least tolerate, if not enjoy the company of kids," says Siegal, who admits he's taken some heat from fanciers of the 90 or so AKC-recognized breeds he did not include. "I really wanted to provide a great variety in terms of price, size and amount of space each dog needs."

In his defense, Siegal acknowledges that there's no guarantee that every dog of the breeds mentioned will love kids, or that dogs of breeds not included won't. He remains generally satisfied, however, with his selections, which run from smaller dogs like the pug and Boston terrier up to giants like the Irish wolfhound and Great Dane.

"I do regret having left out Doberman pinschers, although I did it purposely," he says. "I'm really a great admirer of the breed, but if they're badly bred or improperly handled, they can become dangerous. And I don't want to get sued."

One of the keys to choosing the right dog for a particular family, says Siegal, is to make the actual selection without the children's presence. "There is no such thing," he writes, "as an ugly puppy."

Dogs should be selected not on the basis of what they look like at 8 or 12 weeks, but on the basis of what they will look like (and act and behave) when they're 2, 4 or 6 years old. Children (and, unfortunately, some adults), are incapable of making that key differentiation.

Similarly, dogs ought not to be purchased for a single child (unless it's an only child), but for the family as a whole, lest the children end up competing -- as they probably will anyway -- for the animal's attention.

"The beauty of the dog we have now a Cavalier King Charles spaniel, which is much more chic, Siegal insists, than his family and was obtained almost by accident is that it's a breed that doesn't fixate on one person. She makes each child feel like she's his or her particular pet at different times.

"And that's good, because there's nothing quite like having three children in three different parts of the house call the dog at the same time and wait to see who it comes to."

Unlike many dog experts, Siegal sees no "right age" for a child when the family gets a dog, "since the dog should not belong to the child, but to the entire family." Because he will not permit any of his three children to assert ownership over the family dog, his older son and daughter end up competing instead, he says, for the attention of the youngest child. In a single-child household, he does allow that 6 or 7 is probably a good age to introduce a dog.

But there's more to picking a dog for the kids than choosing a breed that's not too big nor too expensive, and easy to housebreak. "You have to consider the child's personality as well as the dog's," stresses Siegal. Nevertheless, "I can't imagine a child that wouldn't benefit from having a dog."