If you’re going to write a parenting book, you need to remember how human life is made up of phases. So very many of them and in so many different ways.

Moreover, those phases are never quite so starkly defined – or so quickly gone – as at the beginning of our development.

We start out gauging human life in mere days and weeks. For instance, there’s conception. Day 1.

The heart is beating by Day 18. And Day 42 brings with it a functioning brain, complete skeleton and reflex abilities.

At seven weeks, a baby may very well be sucking his or her thumb. At 11, he or she has teeny tiny fingernails to show off on those teeny tiny fingers.

In short, each day or week brings about something amazingly new and precious.

Then the chart changes to months: Four and a half months after conception, unborn babies are showing off what their mamas gave ‘em. At five, they weigh a full pound and are 10 inches long.

This month-by-month tracking doesn’t change after birth either, leaving proud and nervous parents to record such mini milestones as when their children:

• Can hold the weight of their own cute little heads…

• Start to roll over…

• Start to crawl…

• Start to babble…

After that first, often nerve-wracking 12 months, it’s on to measuring years marked by walking, toddling, the terrible twos, preschool, kindergarten, first grade, second grade, third grade and beyond.

And that’s just the simple rundown. Ask a teacher or psychologist or psychiatrist, and they can easily make your head spin talking about Piaget’s cognitive stages of development, Vygotsky’s competing model, nurture vs. nature, and all that good stuff.

Clearly, there’s plenty to ponder if you want to write a parenting book.

One way or the other, it simply makes sense to say that children require different types of nutrients, supervision and attention depending on the phase they’re in. This is key information to keep in mind when writing a parenting book – for your readers’ sake, their children’s and your own.

Exact markets matter when writing a parenting book.

If you want to write a parenting book that covers everything from pregnancy tests to your final child’s graduation, there’s no law against it. But it might not be your best option.

Parenting (as you probably know) is full of phases, not to mention personalities, circumstances, settings and so many other factors. As such, a parent with an autistic teenager isn’t going to need the same advice as a sleepless couple with a colicky infant.

That’s why you want to be as specific as possible with the parenting market you want to reach. And not just because your potential readers might otherwise pass you up for something more specific.

There’s also this fact to consider…

There are plenty of other parenting books out there on the market already, some of which were mentioned in Tuesday’s writing Definition. So what’s so special about yours?

Why should moms and dads pick up your words of wisdom over someone else’s?

While answering the two questions above, keep in mind that those moms and dads only have so much time to work with. So do everyone a favor and let them know right away whether you’re the right go-to for them or not.

Pick an age or age range.

Pick a specific topic, whether it’s a physical concern, mental, spiritual, emotional or psychological one.

Then make it happen.

If you really want to write a parenting book that sells, that’s the formula you probably want to follow.