There's an unspoken set of 'rules' teenagers religiously follow on Instagram.

"I reckon a main influence of what both boys and girls post on Instagram is how it will look on their 'feed,'" Caitlin* explained. "Like, on their Instagram page."

OH, YES! I've heard about this.

Some people have a 'white' theme, where every photo they post is white and bright with bold edges and lots of negative space. Others are more into their 'pastels', with brightly-coloured images of places and clothes and food.

This is Instagrammer Sahara Ray's feed:

I would probably describe the theme as 'skin?' Or 'naked?' But whatever, it's definitely a theme.

"You want to have more followers than you follow," said Caitlin.

But... but... I'm never going to have enough people follow me to justify the hundreds of D-grade celebrities I need to be following. That's not fair.

Obviously, for 'social media influencers', this isn't a problem. Jessica Stein, who runs the wildly successful Instagram account tuulavintage has 2.4 million followers. She follows 224 people. She is so, so, impossibly cool.

But teenagers need a strong ratio too. Even if it's randoms following them, they need to be followed more than they follow.

You must post during prime time.

"There are rules about prime time, of course," explains Caitlin. "It's between 5-7pm, and that's when you're going to get the most likes."

It's... genius.

Caitlin said most of her peers would save a picture to post within this window, because otherwise it's a bit of a waste.

And when it comes to likes, you need to maintain a strong average. "As for standards of likes and stuff - that matters to a LOT of people, but it sort of depends on the rest of your Instas," said Caitlin. "Like say on average you get 150, then if it's less than that, it's bad."

So there's a social payoff for posting during prime time. You're more likely to rake in an appropriate amount of likes, because more people are going to see it.

And if you post a photo and it completely bombs? "You delete it." Obviously.

You need to know what your 'gram is. And don't get confused.

I specifically wanted to know about the rules when it comes to health, fitness, wellness and 'inspiration.' This seems like a huge trend on Instagram, and I was interested in whether everyone can join in.

"I find it lame when an average person tries to be inspirational with some quote that has only a bit of relevance to the photo," said Caitlin.

Meeeee tooooo.

"But with health and fitness stuff," she continued, "you kinda have to have your whole 'gram based around that if you're gonna post those kinda 'grams, otherwise it's lame."

That's surprising. The 'rules' don't necessarily approve of health and fitness content filtering down to everyone's accounts, and instead, it's reserved for designated spaces.