All the steps are now nicely described in the Android developer site available at http://developer.android.com/develop/index.html
Set up your development environment
The main tool used in order to develop, test and package your application is the ADT(Android Developer Tool” available as Eclipse IDE plugin (Please note that as the time I am writing this note, the Android Studio IDE is available on early access preview)
You will need as well the Android SDK Manager in order to quickly manage your installed Android platform, documentation, samples and Google APIs (manages the Android version from 1.5 to 4.0)
The AVD Manager (Android Virtual Manager) will help you to create different Android emulators by giving the Android platform, the size, the amount of memory and other properties.
All those tools are packaged and available in a bundle at http://developer.android.com/sdk/index.html. Al l you need is to extract the archive and launch eclipse.
Building your first application
Before building your first application, you need to know your targeted platform (up to which version you have tested your application), and your minimal platform (you can have statistics about running target at http://developer.android.com/about/dashboards/index.html).
Help on building your first application is available at http://developer.android.com/training/index.html
Running your application
The Android bundle contains the AVD Manager that enables you to configure and run emulators. You can as well run the application in a real device connected by USB.
Help on running your application is available at http://developer.android.com/training/basics/firstapp/running-app.html.
Deploying your application
In order to deploy your application you can just send you generate apk file to any android device or upload this file in Google Play (in case you publish to Google Play, you will need to have an account in Google Play and sign you package).