Android - Handling android libraries (jars) in project

Question

We face lot of problems while dealing with libraries in android project. Problems can be :

1. Regarding versions of libraries added.
2. Duplication of libraries in current app and library app.
3. Sometimes we have to add library in build path sometimes we don't.
4. Some times we have to change version number from project.properties file.
5. We do lot of miner tweaking with libraries to make project run.
6. But I don't have any crystal clear idea about what to do when about libraries which you are using in android app.

Please suggest me site or if you can explain tips for using libraries in android.