It's not complicated at all for men. Without getting into the details, the easiest rule of thumb when wearing a suit is that materials should match. Match your leathers, your metals, and whatever fabric your suit is (which is pretty obvious, unless you're mixing jackets and pants, which is either easy as hell or a voyage into a Land of Danger if you don't know what you're doing).

The only areas of difficulty are silks and socks. Matching a tie with a shirt has its own formulas (if you're not confident, always have the color of your shirt in the foreground of the tie and a color in your suit in the background), but people have trouble when it comes to pocket squares, ties, and silk knots. Never match your tie with your pocket square. Feel free to coordinate them, but if your tie comes with a matching pocket square, don't use it (keep it around, it might look nice with other ties/shirts/suits). As for silk knots, you should link them to a color in your tie, but don't feel the need to make them match. Alternately, you can just throw them out and buy some cufflinks.

Finally, socks. If you're very conservative in your dress, the old rule is to match socks to pants (if impossible, the socks must be darker than the pants). This is because the socks are, for all intents and purposes, extending the pants. If standing, your socks should never show, and even when sitting they will barely show, unless you have your ankle on your knee. However, if you think you've got the confidence and knowhow to have a little more fun with your socks, feel free. If you've got the look and skin tone to pull off black at the office, but want to be a bit more colorful so as to not look so funerary, almost any bright but rich color will do. In between your black shoes and black pants, it can be quite stylish to wear deep purple, crimson, or even yellow socks. If you're wearing a brown suit (and please do, they're incredibly underworn and look good on almost everybody), orange looks great. The trick with this is to keep in mind your position and the setting. If you don't have the gravitas and the rank to wear something like this without being questioned, don't bother.

So yeah, simple stuff.