With business casual all the rage in many offices, the pairing of dress shirts and pants is a hot topic. In some ways, this is actually easier than putting together an outfit where you're considering suit (or blazer and pants), shirt, tie, and sometimes pocket square patterns. But still, based on empirical data (a.k.a. what I see when hanging out in clients' closets), a lot of people get it wrong. Below are 7 quick and easy points to keep in mind when selecting a business-casual dress shirt and pants combo.1) Avoid wearing striped pants with just your dress shirt. This tends to look a little "off," like you broke your striped suit apart and wore just the pants themselves.2) If you broke rule #1 and are wearing striped pants with just a dress shirt, don't worry I won't hunt you down. Just promise me that your dress shirt isn't striped too. 3) If your pants have a pattern (plaid, windowpane, check, etc.), go with a solid shirt, and vice versa. Otherwise you border on looking clownish. Some fabrics are "tone-on-tone," which means they have a subtle pattern to their weave, like a herringbone, but are still all one color. Fabrics like that read as solids and are perfectly fine to wear with patterns. See above how, viewed closely, there appears to be a pattern in the shirt, but overall it reads as a solid. 4) If you're very tall, you may want to break up your height by choosing pant and shirt colors that contrast one another, creating a horizontal line at your waist (see above left). On the flip, if you want to look taller, choose combinations where the colors are more similar in depth and intensity so as to create one long line top-to-bottom (above right).5) White goes with everything. In fact, the white dress shirt is a wardrobe cornerstone -- about as important as, say, a belt or a navy blazer. It comes in especially handy on the inevitable running-late mornings when you need to grab-and-go.6) A contrast collar shirt is mostly worn with a suit for a Wall Street-y look. But if you're going to wear it with just dress pants, opt for pants in a dark hue.7) For specific color recommendations, I like brown pants with pink, light blue, ecru and yellow shirts. And gray pants provide a solid anchor to brightly colored or boldly patterned shirts.Do you have trouble pairing dress shirts and pants? Leave me a comment or question below. I'd love to hear what's on your mind.Images via Mr. Porter and Bonobos.