Good practice is to learn from the best. Here is a podcast with Jake Wharton where he mentions the libs and tools he uses.
In short here is the list:
Retrofit: http://square.github.io/retrofit/
Picasso: http://square.github.io/picasso/
Dagger: http://square.github.io/dagger/
OkHttp: http://square.github.io/okhttp/
Butter Knife: http://jakewharton.github.io/butterknife
Robolectric: http://robolectric.org/
AssertJ Android: http://square.github.io/assertj-android
One more addition to the Wharton's list is:
Parcelabler (online tool for generating parcelable versions of your classes): http://www.parcelabler.com/