To create an android app, you'll need to learn Android Programming language (Nearly exactly the same as 'Java Programming Language', so if you learn Java, you'll learn so much for Android, only a few differences
HERE'S ALL THE INFO
Download and Install the "Java Development Kit" (JDK).
Download and install the "Android SDK".
NOTE: DO NOT install the android sdk in a directory on your computer that has spaces (E.g: Don't install it in C:\Program Files\Android\android-sdk because there is a SPACE between 'Program' and 'Files' in "Program Files". Instead, you can install it in a location like C:\android-sdk which is where I installed it).
Download and install an IDE for Java Developers. "Eclipse IDE" is the best one as for now, recommended by Android.
You can download either "Eclipse IDE for Java EE Developers" or "Eclipse IDE for Java Developers".
Java EE has got more features but a little more bigger in space, but that doesn't matter.
Download Eclipse IDE for Java EE Developers here: Windows 32-bit (x86) version or Windows 64-bit (x64) version OR
Go to this link to view the full list of Eclipse downloads or the latest version if you are viewing this post late.
After installing Eclipse, you'll need to download and install the "ADT plugin".
To do this, open up Eclipse and go to Help > Install new software... Click on Add.
For Name:, write ADT Plugin
Click OK and let it install.
After the ADT plugin is installed, you need to locate the Android SDK in Eclipse (This is what you installed in Step 2).
To do this, go to Window > Preferences and click on / highlight Android.
Under SDK Location:, browse to your android sdk directory.
Remember, I said, I installed it in C:\android-sdk. Locate it where you installed the SDK.
Now you'll need to build your virtual device so that, when building your app, you can view and use your app on your computer to see how it looks like. It's like an android simulator to test your app.
To do this, go to Window > Android SDK and AVD Manager. Click on New... and input your:
to identify your AVD.
to specify your android version (use the version that you're going to create an app which is 'what platform version and above of android does your app require to run - click here to view the versions that most people have so that your app is compatible with a greater audience of people - as you can see from the chart, it is a good idea to use version Android 2.1 (API Level 7) or maybe Android 2.2 (API Level 8) if you're app is going to be more crazy/advanced and use alot more features with the disadvantage of reaching 17.5% less of the android audience. Remember, the less the version, some really advanced things might not work, so you'll have to find a different way around to write some features.
SD Card Size
100mb (MiB) is more than enough.
For Built-in under Skin
it's best to use HVGA.
After you're done creating it by clicking Create AVD, select it, and click Start... to see if it works.
NOTE: it might take quite a long time, depending on your computer.
You're done and ready to create your app. Start a New project before you start learning through tutorials.
Go to File > New > Project... and select Android > Android project and click Finish.
Name of the folder in your computer of your project.
Minimum android version to use your app, as explained before in Step 6.
Name of your App (What it shows like in the Android Market and on the phone menu).
Unique package name for android to identify your app on the market.
Use this format: com.companyname.appname (It has to have com at the beginning. For companyname write your company name and For appname write your App's name.
The main activity of your app (If you don't understand, just type Main or MyMain or MainActivity or something)
Min SDK Version:
This should be done automatically if you selected you're 'Build Target'. If not, just type in the API level of your Build Target.
Here's Overview videos of all these 7 steps: The video has a few more things which you might want to do to troubleshoot problems.
List of really good Tutorials:
You can find a lot more by just searching. But, these videos shall do anyway, unless ofcourse you're looking to create the most advanced app.
Sign-Up to this forum if you get stuck and need help creating/coding your app: