Explore Android API Demos:
Just import the API demos in Eclipse, contained in Android SDK. You need to know how they build the applications. It will clean your most of confusions.
Android Application Structure:
Need to have knowledge about android application structure. You get the help from android API demos.
Strong OOP Concepts:
You need to have strong OO concept, other wise you will be confused early or later.
Java Programming Concepts:
Need to have programming concept in java. Currently we only can develop android applications in java.
Optimize Memory Resources:
You need to understand clearly that mobile apps are different from desktop and web application. So try to use less memory resources. I have attached link, consider it if you have time.
Designing for Performance: http://d.android.com/guide/practices/design/performance.html
Explore Android Documentation:
At the end you get all help about android from its online or offline documentation.
Note:
Above mentioned points are necessary to develop a Android application, might be I have missed some points you can help me out. Waiting for your feed back
