3D picking in opengl

1st of all hello everyone i am very new here..

Recently i started looking into android programming and opengl.
Not a long time passed when I ran into the problem of "3d picking"/ray-sphere intersection.
I have a game in progress in which i'm trying to implement a ray to go into the 3d world of the game on return the object i last pressed.

If anyone knows about this problem and perhaps a solution, plz.. help.. :((
there are a rare number of tutorials on the subject of very low quality and I reading the books about the subject will take time.

In the hope someone here knows the subject and can help i'd love to publish specific code.