Suits come in very different styles and it's really up to your taste to choose what you like.
But, if you want a CLASSIC elegant style (say, for an important event), well you should be careful about some things, regardless of your taste.
A bit of advice from Italy:
- Avoid white-collared shirts unless they're actually white shirts. I know they're quite common in business attire in the US. This doesn't change that they're not ok for an elegant occasion. Shirt should be either completely white or completely light blue. Full stop.
- Shoes and belt should have matching colors. And this color should be either black or dark brown (and the latter not in the evening).
- And while we're at it, no brown shoes/belt if your suit is blue, unless it's very, very dark.
- Socks: always long and they should match either the suit color or the shoe color. NB Dark blue and black do not match.
- The most difficult part is how your jacket fits on the back of your neck. A suit might be nice, but if that part stays too high and does not rest perfectly on your shirt, it will show it's cheap and poorly chosen.
- Appropriate sleeve length for both shirt and jacket is also essential. If the jacket sleeve covers the shirt's one, it's bad. If the shirt's sleeve sticks out too much, it's bad.
Also, if you're wearing a watch:
https://s-media-cache-ak0.pinimg.com...b5b41c3eef.jpg (left: ok; right: not ok)
- There are many collar styles and tie-knot styles. Try to match them appropriately. And btw, never wear a tie with a button-down shirt.
- The tip of your tie should barely reach the belt. It's ok if it's slightly higher, not ok if it's lower.
- If you wear a waistcoat, leave the bottom button undone.