Organize it in whatever way makes the most sense to you. There's no 100% correct way to organize an Android project... it depends on a number of factors (i.e. the size of your project).
If you want to see how Google organizes their projects, take a look at the Google I/O 2012 source code. In particular, check out the iosched.util package... it gives a number of ways to reuse code across your project (mostly by using static utility helper methods).
