Q. "My child is 7 and comes home from school alone, which she loves to do -- a three-block walk.

"She is senible and the neighborhood is safe, but the incidents in Atlanta have made me realize how important it is to warn her about strangers. I've mentioned it, of course, but I don't know how to emphasize it and still have her be a happy, trusting child. How does a parent help a child be both cautious and friendly?"

A. Parents spend their whole careers walking one kind of knife edge or another and this is one of the sharpest.

It's essential that a child realize that the great big world is sometimes dangerous so she (and certainly he) can deal with it.

The Atlanta story can be a peg for this critical subject because, as terrifying as it is, a child has to know it can happen anywhere.

It would be best to read about it together in the newspaper with enough long pauses to let her bring her questions forward, and then to wonder why, with all the wonderful people in the world, there are some mad ones too.

And from there you tell your child that every place has its disturbed people and since they are so hard to recognize it's best not to try. Instead you'll ask her to reject the kind of offers this person would make. It's much easier if she is tought to say "no" to an act rather than to a person, especially since most child molesters are known by their victims.

There is at least a 1-in-4 chance that your daughter will be molested in some way before she is 18 and usually by a friend, a neighbor or a relative. And boys don't fare too well either.

You have to make it clear that she must be wary of all strange suggestions, even though they may be quite innocent.

Some can be avoided entirely if you tell your child -- girl or boy -- that she or he should never even make eye contact with a stranger and always come home at the time and by the route expected. This means that she can't get into anyone's car without your permission, whether she knows them or not, or whether there is an offer of candy or comic books. She shouldn't even get into the car if it's raining, or she's told by the driver that you sent him to pick her up for a family emergency.

And yes, this may make your daughter walk home in a terrible rainstorm, or inconvenience you when you can't have a friend fetch her, but this won't happen very often. For this you make contingency plans by telling your child exactly who is authorized to give her a ride.

You also should tell her that she can't go into the home of a neighbor, even if she's offered milk and homemade cookies, unless the neighbor is on your approved list. Even then, your child must call you first.

What you're actually doing is helping your child say "no" automatically before her conscience does it for her -- a process that isn't fully reliable until the early or mid-teens. Until then she only can depend on supervision and this early warning system.

To develop good radar, your child must know how much she counts.

She has to have strong self-esteem, so she won't tumble to flattery; know that she has rights, and know that a grownup doesn't always know best, especially when he puts his hand beneath her clothes or makes her swear to keep a secret about a little game he knows.

Your child needs to know that her body is her own. Nobody has the right to touch it, or tell her to show it, and if that happens she should know that you want her to say NO and maybe yell and run, even if she has to run to a stranger. The likelihood of two perverts working the same block is rare.

Fear plays a big part in a child's acquiescence -- fear that she will look like a baby; fear that her parents will get mad at her, or laugh, or think she invited it; fear that there will be a terrible scene with the abuser, or that this person really will hurt her if she tells. It can hurt her a lot more if she doesn't tell, and she must know this. Even the indication of unwanted sex will burden and shame a child.

When she knows her rights, and what to avoid, it won't seem so scary to object. And if her opinions about other subjects have been heard and respected she will dare to tell you when she's afraid of someone because he looks at her funny or he likes to tickle her tummy.

At this point you thank her, without any criticism, and never, ever say, "Come now," or "You known Mr. Brown didn't say that!" - or "How could you say such a thing about your own grandfather?"

Remember: A young child almost never makes up a story of sexual abuse, of even the mildest sort.

After the slightest misadventure, it is your job as a parent to tell the adult -- or the teen-ager -- that your daughter was frightened by him and he must never do that again. And if he tried something serious, you must talk with him about it specifically and directly and be as non-hysterical as possible. Even if you're talking to a member of the family.

When the person denies it -- which is almost inevitable -- you say you still want him to stay away from your child; that if she is scared of him that is reason enough to keep a distance. (And it is.) This is a non-negotiable point.

For more on the subject, and to learn how to set up a "helping hands" program of safe houses in your neighborhood, there is The Silent Children by Linda Tschirhart Sanford (Doubleday, $12.95). It's an excellent guide for parents of both boys and girls.

Q. "We plan to take our 2-year-old to Portugal and Spain -- her first trip abroad. We want this holiday to be good for all of us, especially our daughter. What can we expect and how can we get the most out of it?"

A. Your little girl is sure to enjoy the sights, such as the pigeons in the park and the blue and red cars. She also will like the exciting things to do, like jumping on your hotel bed and hearing you read her favorite stories.

Remember: a 2-year-old is the ultimate egocentric, so most of her pleasure will come from having her parents all to herself.

To get the most out of the trip, there is Fielding's Guide to Traveling With Children in Europe (revised) by Leila Hadley (Morrow, $9.95), which your bookseller can order for you.