Make sure your pants sit belted at your hipbone, with the waistband loose enough to stick a finger in. Make sure that whatever cut you choose fits comfortably loosely through the hip and thigh, with enough space that you can move freely without binding or bulging. They should hang straight down off your hips and butt.
Find shirts that are just the right width and length so that the hem hangs fairly loosely around whatever part of your hips it lands on without bunching or riding up - this might mean a shorter cut than you're accustomed to wearing. I find that longer shirts tend to bunch up a lot if I wear the right size.
Consider wearing an outer layer on your upper body that gives the illusion of additional width in the shoulders and torso - a buttonup, a track jacket, a denim or leather jacket. Make sure that this layer fits correctly at the shoulder but hangs loosely throughout the length, meeting up with your pants to form a straight line. It might help to leave it open. The goal is to widen your torso so your hips look more proportional.
Basically, you're not going to narrow your hips unless you get compression shorts, and those have only limited effect. So since you can't make your hips fit your body, you make the rest of your body fit your hips.
(This only works if your hips are within the male range for your height for guys who could plausibly be in the same weight range as you. It will make you look somewhat heavier than you are, but mostly in illusory upper body mass which is fine. In general, I'd say as long as your hips are narrower than your shoulders - as long as your arms hang more or less straight at your sides - you can do it this way. If you're very very pear shaped, you'll need a different strategy.)
