1. You eventually want to own three suits. Your first suit should be either navy blue or gray, possibly with a light chalk stripe (like a pinstripe, but softer), and in an all-season, medium weight. Either of these colors will fit into most social settings. Your second suit should be the one you didn’t get the first time around. Your third should be black – not for funerals, but for black tie affairs. If you work in a field where suits are the norm, you’ll probably want more than three; once you’ve covered the basics, you can move on to more distinctive suits (pinstripes, different weights, unconventional colors, etc.).
2. Suits are made of wool or cotton. Higher thread counts signify higher quality, but are ironically not as durable, so stick with something mid-range. Ask the salesperson to help you with this. (Yes, ask the salesperson. Suits are not self-serve.) Synthetic fibers need not apply.
3. You never button the bottom button. Apparently, Edward VII got fat and couldn’t button his vest over his belly, so now nobody does. On a three-button jacket, you button the middle; the top button is optional. If you have a jacket with 4 or more button, you obviously know what you’re doing already.
4. A gentleman carries a handkerchief in his front breast pocket. You don’t have to get fancy, just fold it square to fit and have 1/4” to 1/2” sticking out the top. Then proffer it as needed. And wash it after.