Professionalism can lead to respect, raises, promotions and better performance. It's not a single act, but a collection of behaviors and presentations that show you're dependable, focused on your work, understand how to coexist with all kinds of different people in a respectable manner and open to improvement. A lack of professionalism will likely cause your career to stall out soon after it shifts into first.
Show Up to Work
You're only human! Family emergencies happen, and illnesses and important engagements can keep you from work occasionally. However, try to keep your absences to a minimum and certainly in line with the number of sick days and personal days you have. Constantly arriving late or taking off tells your employer you don't take your job very seriously and don't much care about your co-workers or the company. If you do need to take a day off, tell your manager or the appropriate person in advance. If you can't get to work on time due to a scheduling conflict, talk to your manager about changing your scheduled start time.
Whether you're a manager who appraises his employees every six months or an employee who's trying to help a co-worker improve, your use of tact to diffuse awkward and tense situations is a sure sign of professionalism. Avoid the brutal truth, and instead look to approach situations diplomatically. For example, suppose an employee of yours needs to work on getting his tasks done in a timelier manner. Don't tell him he has poor time management skills or infer that he's lazy. Instead, take the more professional approach: explain that you've noticed he often experiences delays in completing his work, and then have a two-way conversation on how he can improve.
Your body language plays a huge part in professionalism. Slouch down in an interview and you suddenly look like you don't care about getting the job. Shifty eyes send a message that you lack confidence. A stoned-faced expression when you're trying to help a struggling employee makes it seem that you lack empathy. When you're in a meeting or talking to someone, sit or stand up straight, maintain regular eye contact while you speak and when you're listening and match your facial expressions with the type of emotion you want to convey.
Verbal and Written Communication
Exude professionalism by speaking clearly no matter who you're talking to. Remember that communication is a two-way street, so allow the other person or people to reciprocate, and always listen. Don't think about what you're going to say next or let their words go in one ear and out the other. Your written communications should similarly reflect your professionalism. Avoid excessive use of acronyms and jargon, avoid emoticons and get to the point without being too blunt. Read over everything you write to make sure your message is clear and your tone won't be misread as being harsh or unfriendly.
Your dress and appearance immediately tells others if you take a professional approach to your job. Wearing khakis when the dress code calls for business formal, for example, screams unprofessional. In contrast, dressing in a full suit in a business casual environment shows that you don't care about the workplace culture, and it might even signal to others that you're attempting to stand out.
Open to Criticism
Closing yourself off to criticism or responding poorly to it tells others you're not professional enough to acknowledge any imperfections. Be open to criticism. That goes for managers and employees alike. Although managers are often thought of as doling out criticism, the best and most professional ones accept criticism from their employees as well. If you disagree with the criticism, acknowledge it, but don't immediately rebuke it or say something you might regret. Take a day or two and think it over. You might find there's some truth in what was said.
A professional employee is a dependable employee who makes good on his promises. Complete projects and tasks on time and at a consistently high level. Put forth your best effort no matter what you do, even if you consider the undertaking small and insignificant. Make sure your word is gold and that you don't promise something you can't fulfill.