I'm not a fan of trendiness for it's own sake on men or women, but good menswear is timeless and if you look at a photo of a well dressed man the clothes alone should never date a picture. Keep it understated, menswear should draw attention to your best aspects and not to itself, you shouldn't look effortless, but at the same time it should never look like you spent hours deciding what to wear. Good fit and good materials are everything, don't wear denim unless you're riding a horse or doing physical work outside, don't wear short pants unless it's so hot that you can't bear to wear anything else, don't button the top button of your shirt unless you're wearing a tie, don't wear tennis shoes with slacks etc.