Use Freehand lasso for a drawn outline, Polygon lasso for straight segments, or Magic wand for connected similar colors. These added tools support documents up to 8 megapixels; reduce larger documents first.
Refine the edge at a close zoom. Hair, glass and soft shadows need manual attention; a one-click result is a starting point, not a guaranteed clean cutout.
Choose Keep selected pixels or Remove selected pixels for direct pixel edits, after duplicating the source. Choose Selection to layer mask for a separately editable mask. PNG keeps transparency; JPG is opaque.