I attempt to look cute in my suits by wearing pretty tops underneath, (ie, pink or something pattered to add interest) and by wearing shoes that have some details or stand out.
Also, well-cut, subtly pinstriped suits look great on women!
Try to stay away from plain white shirts (too boring) and make sure that your blouses are neatly pressed. Go for feminine jewelry. I like to wear my diamond studs and my Tiffany heart necklace when I am doing the business professional look. Also, wear heels or pumps. Stay away from clunky shoes or flats. Also, don't forget to apply pretty/natural looking makeup. It drives me nuts when I see a woman in a nice suit with no makeup on wearing a white shirt that has a nasty wrinkled collar and orthopaedic looking shoes. Why bother even put the suit on?
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"Whatever you are, be a good one." --Abraham Lincoln
i agree w/ everything the girls have already said. also, try bcbg, tahari and nanette lepore for suits. all those labels carry suits that really fit properly, my pet peeve is when i see women wearing suits that are too boxy and just plain don't fit.
one word of warning though--make sure you don't look "too" cute, it may sometimes undermine your credibility, which sucks and i could write forever about how unfair that is but c'est la vie, i guess.
I really like tahari and theory. They use really nice stretch wools which are really professional and crisp, but still very comfortable for a long day at the office. If you are pressed for time and need to order online, J Crew has pants which come in a variety of shapes and styles. I find their jackets require tailoring to fit me properly, but they are very good quality wool and comfortable.
As someone who works in a conservative, but slightly less formal office, I notice a lot of people here really play with accessories and shoes. Fun shoes in a bright color can perk up a really tired suit. Also, if you are not taking your jacket off and you have a pretty silk shell or cami, that's a gorgeous look.
What are you getting dressed up for? I should also add the caveat that I work in a law firm, so I might be out of touch with what is appropriate in less conservative offices. HTH!
I'd throw on a pretty brooch or a long strand of pearls wrapped around a few times. I also like wearing a cute cami underneath instead of a button down shirt, but that may not fly in a very corporate environment. Starting off with a suit that fits well or is tailored to fit you perfectly will automatically start making you look/feel more feminine than just wearing a boxy suit that doesn't fit like it should.
It's definitely all about the accessories as many other girls have mentioned. Pretty and distinct jewelry and great shoes. You could also add a scarf.
Also, feminine blouses (not necessarily camis) instead of button-downs, in fun colors and patterns. A subtle mix of patterns would be nice, too. For example, a charcoal grey pinstripe suit with a floral top or even a striped top.