When you have started up your view and haven't applied any transformations the axis are aligned like this: The x-axis goes from left to right, the y-axis comes from the bottom and goes up and the z-axis is moving from the back of the screen towards the front of the screen.

Rotate

public abstract void glRotatef(float angle, float x, float y, float z)//OpenGL 

The angle value is the number of degrees to rotate. 





If you look from the positive end towards the origin of the axis the positive 
rotation is counter-clockwise.

Your other fingers will now point in the positive direction of the rotation over that axis.