First impressions count– especially when it comes to your attire for occasions like the first day of a new job.

In a recent post by CNBC Make It, workplace stylists Jacci Jaye and Alexandra Suzanne Greenawalt, highlighted a few of the most important ‘do’s’ and ‘don’ts’ to follow when it comes to dressing appropriately for work.

One important ‘do’ to follow is investing in a custom suit, Jaye tells CNBC Make It. Customs suits tend to have a reputation of being more expensive than those that are not, but because these suits are tailored to fit your body type specifically they often look better on you and produce a more polished look.

“Sometimes you’ll find there isn’t much of a price difference between a custom suit and one you buy off the rack,” Jaye said. “So you might as well invest in one that’s custom.”

However, if you opt for purchasing a suit off the rack the stylist says you should choose one that is tailored because the fit of the suit is more important. She tells CNBC Make It that expensive suits can look very cheap if they aren’t tailored properly and vice versa for cheaper suits.

While suits can offer a polished professional look, Jaye says that pant suits, in particular, are not “modern or flattering.” Instead, she suggests that women wear dresses or a dress paired with a matching jacket. It is important to keep in mind that dresses or skirts should be no shorter than two inches above the knee. Women should also keep in mind to purchase proper shape wear, which sleeks the body, she said. In addition, hosiery should always be worn. “No bare legs.”

The choice of office wear for men is much simpler. The stylists suggest that men wear a button down shirt with a blazer, paired with nice trouser and loafers.

When it comes to fashion ‘don’ts’ Greenawalt says the most important things not to do include avoiding dressing too provocatively, wearing too tight or too loose clothing, items that are stained or have holes, sweatpants and casual shorts or t-shirts. You should also avoid distressed or light colored denim, flip-flops, sneakers, hoodies and clothes with logos or neon colors, Jaye added.

“Ask yourself, what purpose does this clothing serve?” Jaye told CNBC Make It. “Flip-flops have a purpose for the beach. Gym sneakers have a purpose for the gym.”

Other ‘don’ts’ include executives wearing open-toed shoes, and men wearing low-step shoes with suits. In general, it is important that your clothes are ironed and wrinkle-free.

While a good outfit is a great confidence booster, it can also influence the way others perceive you.