Hitting a million downloads is a major milestone for an app developer. If you were a rock star you'd be going platinum. If you've hit a million downloads you know you're onto a great idea!

Take a moment. Ask yourself who do I think of as a leader? What pops into your mind?

However, sometimes having a great idea isn't enough. The app market is swamped with great ideas that just never get that much interest. Why?

Adrian Hon, CEO of Six to Start, says it could be:

Because the market isn't ready for your app yet

It's too similar to another popular app

Cost is turning people off

Bad reviews are killing any progress

Adrian overcame many of these pitfalls himself when launching his first fitness app Zombies, Run! But, with nearly 4 million downloads to date, he seems to have cracked the formula to app store success.

Here are his five top tips to hit the 1m download mark...

1. Spotting a killer idea

Obviously, one of the first things to do is to check the relevant app stores to find out if anything similar already exists. You don't want to be leaping into an overcrowded market. Yet, if you find nothing even similar, it might be a sign that your idea just isn't ripe yet.

If the idea holds up at this stage, consider whether you have the skills and resources to make the app. The bar for quality has shot up over the years - apps that were impressive three years ago are run-of-the-mill now. When hundreds of new free apps are released every day, you have to be very special to stand out.

Finally, remember that this app idea may take years to come to fruition, so ensure it's something you love. I like running to keep fit, but I found it boring. I created Zombies, Run! with lead writer Naomi Alderman because we wanted to solve problems we'd had in the past and make running more fun. Find an app idea you'd enjoy using then you really will be working for yourself.

2. Testing the water

You'll often hear app developers saying that the only way to measure the popularity of your app idea is to launch it and see.

I disagree.

There is a way to test your app idea on a paying market without developing a single line of code! All you need is to create a demo. Then you can launch your crowdfunding campaign.

Not only does crowdfunding help raise the money to develop the full app, it allows you to test your idea on a paying audience. In return, they get a copy of your app once it's been developed.

For example, when we launched Zombies, Run! we gained around 3,500 backers and smashed our initial target. More importantly, we got the validation we needed for our idea.

Now we're doing the same for our next project.

The greatest power of crowdfunding is that it allows you to create an engaged community, from scratch, in a relatively short period of time. These 3,500 people wanted to see our app become a success so they could see the game come to life and get their hands on a copy. They had skin in the game. So, they were a great support when it came to getting the app out there.

3. Getting paid for your work

As altruistic as we may be, we still need to get paid for our work. But finding success with a paid or subscription model app is hard with so many free apps and games in the market.

When we launched Zombies, Run! back in 2012, it cost $7.99 - a pretty high price at the time but, as most apps were paid, it wasn't that unusual. Today, the vast majority of new apps are free, especially the most popular ones. It's simple - making your app free reduces the barrier to entry, and helps easily find out whether it's something people will pay for.

In 2015, we made Zombies, Run! free to download, and let them play one mission a week without paying us anything. If they wanted to remove the audio ads and run more often, we charged a simple $20/year subscription. It was nerve-wracking at first, but now we have tens of thousands of happy subscribers!

So, the short answer to getting paid: Get people hooked on great content, then give them the option to pay for more. They won't be able to resist.

4. Using feedback productively

I see a lot of apps fall at this penultimate hurdle. They launch their app, watch the first 10k downloads trickle in, mark it a success, and then move on to their next idea. Reviews and feedback get pretty much ignored.

But great customer service is the foundation of your app business. If you can respond quickly, clearly and solve the user's issue you'll develop a loyal fanbase.

In fact, we found that by investing in customer support we actually saved money in the longer term, because we fixed all the bugs and streamlined usability based on the feedback. So, when our user base skyrocketed, there were much fewer support issues to deal with.

5. Building on success

Feedback might also provide you with the seed of your next idea. Our charity Racelink platform is completely different to anything we'd made before, but came from the suggestion of one of our users. This led us to develop a whole string of relationships with the UK's biggest charities.

Using feedback to develop new ideas shows your users three things:

1.         You're listening to their feedback - It isn't just a bot replying to reviews with "Thanks for your feedback", you are real people who are really listening.

2.         They're valued - The community is valued as a good source of new ideas which you will actually use.

3.         You're reliable - If you have big plans for the future then you plan to stick around. That means they can rely on you for updates, support, and new features/content. Their $8 isn't going to waste.

If customers feel confident in these key points, they will be confident in spending money on your app.

If I had to sum my advice up in one sentence I would say: Love what you're doing and seek feedback at every step.

If you believe in your app, it has space in the market, and you listen to what your audience want, you'll be on the right track to hit that magic 1 million downloads mark.

Get fit and out run the zombies here