Tips for lightweight Android Applications

I am starting to develop Android applications and I would like to know if there are any tips for creating lightweight applications. This is my first attempt to write applications on a mobile platform but I hope that my experience in programming will help.

I have in mind the "Better, Faster, Lighter Java" book, but will this be "the" answer to my question? Are there any tips specific for the Android Platform that will allow me to build lightweight applications?

Can I build Android apps with Swift?

No. Although the Swift compiler is capable of compiling Swift code that runs on an Android device, it takes a lot more than just the Swift stdlib to write an app. You'd need some sort of framework to build a user interface for your application, which the Swift stdlib does not provide.

A good place to start would be the Designing for Performance and Designing for Responsiveness documents in the Android Developer Documentation.