i wanna to develop a twitter client for Android OS just to update the status and to get friends updates, what is the best way and your recommendations to authenticate the user to be able to access twitter services via my client ?
Depending on your preferences, it might be worth looking into Twitter4J - Twitter4J is a Java library that provides a standard API around the Twitter user web services and provides all the objects you need to tweet, re-tweet, view users timelines, profiles etc.
Twitter authentication is done using OAuth, so you need to register for your application details on the Twitter site.
If you prefer to work with WebServices/JSON then you can just use the direct Twitter Web Services.
When developing the app, you will need to take care to optimize the caching etc, as Twitter limits the number of requests that can be made per hour, and if you dont manage the requests properly you can quite quickly hit the limit.
In Twitter OAuth what should be the " callback " in my case , what i understood that call back is where the flow will go after making the authentication, but i'm developing android application , so what will be the call back in this case , or i should use "desktop" and let the user write down the given PIN ?