1: Everyday suit trousers pair well with a blazer or sport coat in a thicker fabric: wool, corduroy, or tweed.
2: If you go bolder on top—with a pattern, a color, a fabric such as velvet, or double-breasted—keep the pants neutral and solid. Or jeans, if the dress code allows.
3: A solid white shirt and simple tie will ground the look. Don’t contrast a too-light jacket with too-dark pants, or vice versa.