There are some basic rules to suiting up that every guy should know.

Please get suits that fit well (including tailoring) rather than getting suits for the name brand or because they are on sale. Every designer has a different fit. I personally prefer J. Crew's fit, but that's because I'm short and they look out for the little guys (go 34S!). 

DO:

-Make sure the shoulders fit. Shoulders are critical for a perfect fit. You can read more about that here. whatever you think your size is, try one size down from that and see how it fits. 

-Find a good tailor. Google 'best tailors in my city' and check out the reviews. You should build a rapport with your tailor so that he or she eventually knows your style. Before going to the tailor, you should have an idea of what your style is. You should soon get to a place where you tell your tailor exactly what you'd like. Sometimes tailors will let you know their thoughts, and that's fine. As your style game evolves, you'll quickly know what advice to take and when to follow your own vision. 

-Get the pants hemmed. Don't let your pants pool all over your shoes.

-Get the sleeves shortened so that about half an inch of your shirt sleeve is showing. I'm taking a leap of faith that you know I mean long sleeve shirt. Also, this is assuming said shirt sleeve is breaks (ends) at the edge of your wrists. 

DON'T:

-Get a suit with more than 2 buttons (even 3 buttons have rare acceptance in style society)

-Get a suit that's majority polyester (best to avoid completely). Read the care labels before purchasing so you have a better idea of the quality you are investing in. you'll most likely get the quality you pay for.

-Get a suit that doesn't fit in the shoulders (can't stress it enough!). Just don't do it man.

-Get wide lapels if you're short like me (generally speaking). Wide lapels are usually reserved for the 6 footers and above. They can have them. I prefer around a 2.5" lapel width and so should you. If you're 6'0"+ and not slim, then wide lapels may suit you better. 

If you've heard any kind of style advice from anywhere, you probably already know the suit color(s) to start with: navy or gray, depending on your source. You can't go wrong with either one, but I do prefer a heather gray as the first option. Here's how easy it is to pair either of them up with almost any shirt in your closet. 

Check out these options for quality bang-for-buck suits. I'll occasionally add specific suit sales as well.