ShouldersConceal: If you want to appear narrower in the shoulders, wear dark colors on top. Raglan sleeves on shirts also make your shoulders seem slimmer by drawing your eye inward. Avoid wearing anything boxy since this adds weight and does not draw the eye to a defined waist.
Reveal: Wide lapels or epaulets on your jackets will widen the look of your shoulders. Also, wearing anything with strong shoulders and a nipped waist will accentuate your shoulders.
NeckConceal: Audrey Hepburn was admired for her lovely long neck, but if you feel that yours is a little too long, there are ways to conceal it by wearing high crew-neck tops or turtlenecks.
Reveal: If you want the opposite effect, wearing V-necks and wide U-necks will elongate the appearance of your neck by drawing the eye down toward the décolletage.