Apple CEO Tim Cook starts his morning routine at 3:45 a.m. Ellevest CEO and co-founder Sallie Krawcheck starts her morning routine at 4 a.m. So does General Stanley McChrystal. Comparative late bird Jack Dorsey doesn't start his morning routine until 5 a.m.

Clearly, it pays to start early.

But not always. 

Box co-founder Aaron Levie doesn't start his day until 10 a.m. Neither does Reddit co-founder Alexis Ohanian. (Although that may have changed now that he and Serena have a daughter.) In response to Inc. colleague Marcel Schwantes's article highlighting research that showed the world's most successful people start their day at 4 a.m., J.K. Rowling tweeted, "Oh, piss off."

So whom should you emulate if you're trying to follow the perfect morning routine? Cook, Krawcheck, and Dorsey?  Or Levie, Ohanian, and (evidently) Rowling?

None of them. The only thing you should emulate is what they and countless other successful people have done: Create a morning routine that works for you.

How? Start with some basics. Then use the same approach you use for running a business: Evaluate the results and adjust as necessary.

Here we go:

1. Embrace your inner early or late(r) bird.

While early risers tend to claim doing so is a simple matter of willpower and persistence, research shows that nearly half of your chronotype, or internal body clock, is genetic.

Take the circadian rhythm, the process that regulates the sleep-wake cycle. The average person's biological clock runs on a 24.2-hour cycle; instead of a periodic "leap day" to reset ourselves, we tend to adjust a little every day to account for the 12-minute difference. 

Yet some people have internal clocks that run longer than 24.2 hours, and as a result naturally fall asleep later and, over time, get up later.

Which means they didn't decide to be late birds. They are late birds. It's how they're made.

So if starting your morning routine early sounds like hot death, no problem. Correlation -- the fact many successful people start their morning routines extremely early -- isn't causation. Successful people who start their morning routines early aren't necessarily successful as a result. They're successful because they've matched their body clocks to their schedules.

That's your goal. 

As much as the nature of your business and personal life allows, choose to start your day at a time that works best for you. If you aren't sure, experiment. Try 6 a.m. for a week. Then try 6:30 a.m. Or 8 a.m. Or 4:30 a.m. See how it feels, but more important, see how it works.

Because what time you start your morning routine doesn't matter. What matters is what you get done once you do get started.

2. Incorporate a little moderate exercise.

Aerobic training of "moderate intensity," with an average heart rate of around 112 beats a minute -- elevated, sure, but this still falls on the lower-mid end of the cardiovascular intensity scale -- improved participants' moods for up to 12 hours after exercise.

"Moderate intensity aerobic exercise improves mood immediately, and those improvements can last up to 12 hours," says one of the researchers. Which means adding exercise to your morning routine helps ensure you take full advantage of the "happier" 12 hours that follow.

3. Include protein in your first meal.

University of Illinois nutrition professor emeritus Donald Layman recommends consuming at least 30 grams of protein for breakfast. So does Tim Ferriss in The 4-Hour BodyTim recommends getting that 30 grams of protein in within 30 minutes of waking up.

Protein-rich foods keep you full longer than other foods since they take longer to leave the stomach. Protein tends to keep blood-sugar levels steadier and prevent hunger spikes.

Plus, research shows dopamine regulates motivation: in this case, causing you to initiate and persevere.

Which is exactly what you need to do when you wake up: initiate and persevere.

If squeezing 30 grams of protein into a "normal" breakfast sounds daunting, try a protein bar or protein shake. They're a lot more convenient (and tend to include a lot fewer calories).

4. Start your workday with something you really want to do.

Don't check your email; if you do, only deal with truly important issues. (It's easy to confuse "urgent" with "important.") Don't dip into your social media feeds. Don't "ease" your way into your day.

Before you stop working today, plan what you will do first thing tomorrow.  Prime yourself to hit the ground running.

When you knock out an important task first, that sets the tone for the rest of your day. You'll feel really good about yourself -- and will be motivated to accomplish whatever is next on your list.

5. Then evaluate and adjust.

Maybe you'll need to start your morning routine a little earlier to ensure the quiet time necessary to complete your first task. Maybe you'll need to start your morning routine later to ensure you feel rested, refreshed, and "on."

Maybe you'll need to schedule a little exercise for later in the day. Or adjust what you eat.

Or maybe, like Steve Jobs, your morning routine will simply involve asking yourself one question:

For the past 33 years, I have looked in the mirror every morning and asked myself: "If today were the last day of my life, would I want to do what I am about to do today?"

And whenever the answer has been no for too many days in a row, I know I need to change something.

Or maybe -- and this is key -- you'll need to help the people around you adjust to your morning routine. 

You probably don't think of it this way, but everything you do "trains" the people around you how to treat you. Let employees interrupt your meetings or phone calls because of "emergencies" and they'll feel free to interrupt you anytime. Drop what you're doing every time someone calls and they'll always expect immediate attention. Return emails first thing in the morning and people will expect you to respond that way. 

In short, your actions give other people permission to keep you from working the way you work best. So make sure your actions give you the permission to work the way you work best. 

Test, evaluate, adjust as necessary, and make conscious decisions about your morning routine. 

Not a reflexive choice, based on what you've always done. Not a copycat choice, based on what some other successful person does.

Thoughtful, smart, and logical decisions based on what makes you most successful.

Because where your morning routine is concerned -- and the rest of your day -- that's all that matters.