Hi Rui,
Most of the shots I take are taken in spot focus and spot metering or centered weighted metering. I always have the AE lock/AF lock/both setting set for AE lock. That way I can move from the focal point and lock the exposure if I don't like what I see. And yes I do sometimes lock the focus and then compose the image before the shot.
I will post a before and after image tomorrow.
jj