you would meter the sky and for example... if the focus of the pictures are the clouds in the sky den meter the white clouds lor...
basically meter what u want to expose, cause in this case you don;t want to blow out the whites.
if its those sunset sunrise kinda "egg-yolky" sun shots den meter near the sun lor...
you might want to underexpose it even further for shots with the sun in the background.
the subject that is shadowed i.e the siloutte should be blackened out from the pic leaving the outline of the object lor.. hope this helps
oh and one more thing... if you can seem to get the cam to focus on the subject(siloutted figure) you might want to lock the exposure of the sky, den lock the focus of the subject or lock focus den lock exposure lor.. (i prefer the first method)
if u are on a canon SLR system there is AE lock the (*) symbol. you can also do it manually, first meter the sky, get the values (shutter spd and aperture valuses) and input that. den just use that setting and shoot your subject lor. Re-meter if you need to when light changes.