
Look for a great fit, something that makes you feel powerful and comfortable when you're trying it on. Be sure to see how it moves when you walk around and move your arms up and down. If you feel awkward, keep looking. Another great store to check (and these are often located near Ann Taylor, at least where I live) is Banana Republic. Other stores that carry affordable, stylish suits include The Limited, Express and Macy's. Look for dark gray or black in a medium-weight fabric that you can wear for at least 3 seasons, if not year round.
Now for the fun part: Add your personal touch with a beautiful blouse, statement necklace or conservative yet colorful (or otherwise embellished) shoes! You can also mix-and-match the blazer with a pencil skirt and tights, or pair the pants with a nice top and vest (if it's less formal). Browse JCrew.com for style inspiration; you can imitate with less expensive wares.
Suits are generally conservative by nature, so opt for a great fit in the best fabric you can afford, get it tailored, then liven it up with your blouse, jewelry and other accessories.
For more advice, check out the reader comments on this post about what to wear to a job interview.
Readers: If you only had one weekend to shop for a suit on a budget, where would you go?