Marketing

There is a lot of good advice above.
I would add that it is important to plan out your marketing. As others have said start looking at how you are going to market the app from very early on in your development. You need to think how your product fills a customers need. That will define how you will market your product, as you can state with asking yourself a simple question of why would they use it then from there move to looking at (if you can afford it) ad space to target which will hit your demographic and target audience.
Hope that helps a little.

send ans many review request as you can, i'll help if you get your app reviewd.

Marketing plan completely depends on the app life cycle, type and monetization model. There are a lot of tutorials available free in the Internet, but not all actions described there must be applied to all apps. And the most important fact - these articles do not explain how to do it.

If you want to invest into your app`s marketing, evaluate if you are willing to invest a great deal of your time and budget into it. If you are good in developing games, it does not mean that you will also be good in marketing them. If you still want to try, contact successful app developers (you need advices that do work) or contact PR companies that have sufficient experience.

Please contact me via private message if you want to learn more details.

You don't tell us what kind of developer you are. Are you a indie developer or a you work for big shot developer company ?? What is your current financial condition ?? I am asking this because right now I am in the middle of same kind of problem. This problem is much bigger for me because I work in an indie developer group. Our current financial condition is not that good. If you have enough money and don't have any financial crisis like us so you can easily go to a PR company as many people already suggest you. They have various kind of marketing packages and one precaution about this, you have to choose wisely. Because those package are pretty much costly. You also have to launch a campaign about your apps on social media like Facebook, Twitter, Flicker and so on. Participate as many forum as you can. This is very important. Because you can find many potential customer on forum and there are many forum like this one who give extra privilege for developer and also have a section where you can promote your apps. And another thing I should add, try to target your audience. Its pretty much important. Suppose you develop an apps which publish all kind of business related news. Only businessman and wall-street people will like your apps but its no use for a teenager. And one of the most important thing is try to be innovative. Don't be a copycat.

Mobile apps marketing is a complex system, and you need to pay attention all of its aspects. Good luck

In the present time social media is also best for marketing.

If you do marketing for your application then social media is the best way to you. First of all create Twitter account for your application, and locate the movers and shakers in your niche industry, and try to make a connection. Create a Videos app, Videos are the easy and perfect method to show people how cool your application is. Create your own blog or article and publish it.

Reviews are a key item I'd say, you should send your app out to any review site you can big or small, and then hope you get a few nibbles. Doesn't even have to be a full review, sometimes you can get a little blurb out on your game. Your game actually being good is important there too since bad reviews probably aren't going to help your cause.

Whether you are just regarding to release your app, or your application has previously been out and you need to get better your marketing for it, it's a better thought to think about who is probable to be using your app. Market your own website , not your app store pages. Create custom app store links using on your own website. Make in app marketing.