I've recently bought a nikon 50mm prime 1/1.8f lens, and I'm learning about shooting portrait photos.
What I wonder about is how to focus on the eyes while having aperture wide opened at 1/1.8? The technique I know is to focus and recompose, but at such a wide opening the focus gets lost immediately in the process. My Nikon D3300 has only 16 AF points, which means that I should always focus on one of those points without any possibility to change the frame?
Also, which aperture should I choose? As far as I know, I should choose 1.8 for the best bokeh, step down a bit for better sharpness and tolerable bokeh...and try to choose "normal"/smaller apertures while shooting landscapes. How do I know which aperture is needed in which situation?