PERFECT THE FOCUS
There’s less room for error when shooting shallow DOF, so you need to take control of your AF
Be aware that working with shallow depth of field means slight focus errors will ruin a frame. select one focus point instead of a patch. Keep it small and fixed. employ the focus lock using the shutter button half-press or rear focus method. recompose after you lock focus to achieve the composition you want. Look for a hero within the scene, one with strong elements that deserves to own the focus.
Keep a generous amount of background scene so we can enjoy the bokeh.