Have an idea for a killer mobile app? If you forge ahead you'd better do it with your eyes wide open. Nearly four million apps are available for download across the major app stores, with 1.5 million in the Apple App Store and 1.6 million in Google Play, which means getting noticed and catching on with mobile device users won't be easy. If you really want to give your app the best chances for success, take some advice from Ben Rudolph, co-founder of Straw, a social polling app for iOS, Android, and Windows Phone that launched in June. With 12,000 active users and close to 500,000 poll interactions, he says his team did some things right to get traction early on. For one thing, he says there are five questions anyone should ask before building a mobile app.

1. Will the app solve a broad problem?

It might ingeniously do something for you or a niche demographic, but if you're looking for wide adoption, you'll need an idea that will help the masses. "A lot of times people [say], 'I've got a great idea for an app because I have this hole in my life,' or, 'I have this thing that I need done,' but it's something that's unique to them," Rudolph says. "I think the real opportunity is when you create an app and you create a service that actually solves a broad problem."

2. Will the app fundamentally change consumer behavior?

Think of the home-run apps that have done this. For example, when something big happens and a person wants to gauge public sentiment or sound off an opinion, he or she may go to Twitter. And phone-toting young people ubiquitously use Instagram to communicate and share images of their lives with friends and followers. Will your app be one people use once a month or every day? Whatever you build should be something that aims for the latter.

3. Whom are you building it for?

Rudolph and his team created Straw for Windows, iOS, and Android to democratize polling and make it easy for as many people as possible to get advice and opinions from their online communities and the internet. They also built the platform's voting mechanism in HTML5 so everyone--even people who don't have the app--can participate.

To figure out which solution is right for you, think carefully about who the app is for, how those people will use it, and what platforms need to be in play to make it a reality. "For some that might mean HTML5 only. For others, iOS and Android [or] just one of the two," he says. "Don't peanut butter your resources just to check the 'all platforms' box."

4. What do you stand for?

In other words, what's your core culture? "You really need that North Star to say this is the thing that we're trying to accomplish, how we're going to accomplish it, and why we believe it matters," he says. "If you stay true to who you are, what you believe in, and why you're building your product or service, it makes it much easier to prioritize features, marketing, and how you want to engage with your community."

5. Should you monetize it?

With the title of worldwide retail sales evangelism director, Rudolph has a full-time gig at Microsoft, as do the other three co-founders of Straw. "Microsoft has a great moonlighting policy that allows us to do this as a full-blown side project," he says, adding that, for now, the Straw team is focused on growing the app and engaging its community, and that, at some point in the future, it will determine if it makes sense to turn it into a growth business. "We didn't want to just say, 'Hey, we're going to go build a monetization platform built on X strategy,' and then people revolt on it," he says. "[It should] feel like a natural extension of the app and actually increase its usefulness rather than turn people off."