A very big issue people tend to have is mixing their work life with their off time. If you mix the two you may find yourself in a lot trouble down the line. Know what to do and not to do.
The best way to balance your personal life and professional life is to have time management and boundaries. Keep them very separate if you can. As soon as work begins, leave your personal life at your doorstep and when you leave work leave that at the job. Theres nothing worse than everyone at work knowing your business, including your boss. The less everyone knows about you the better. NEVER tell anyone your business at work, keep it on a professional level. Don't tell them about any social networking sites you are on (because you will be looked up at some point).
Theres 2 people in you, the person at work and the person outside of work. Its okay to have more than one side. The problem with everyone knowing the places you hang out, the online sites you are on, if its in any way in breach of contract with your job then its possible for you to be laid off.
If you are calling out sick for reasons other than being sick than cover your bases and keep your ass home! If someone sees you at the mall and your supposed to be sick it will cost you. Also don't blab to your co workers about the party you attended the night before and how you are too hung over to go to work. Keep your story consistent.
The workplace is no different than grade school. Age doesn't matter, there will always be someone that conducts themselves like a high schooler. Miserable people will always want to make others around them miserable and thrive on drama. If there is something you don't want ANYONE to know then simply don't reveal it to anyone in conversation. I hate to break it to you but no one keeps secrets. Tell your co-workers only things you don't mind everyone knowing about you.
Personal calls and episodes need to be taken care of in private. Deal with them away from your work area on your breaks. No emotional breakdowns either, don't look like you aren't capable of keeping it together.
Under NO CIRCUMSTANCES do you fraternize at work. In a lot of places you can also get in trouble with that. Most flings don't last anyways so keep your flirting outside of work and away from someone working at the same place. You don't want to be the talk of the building.
Making associates or friendships are okay, but do that knowing that the more they know about you, the more they can hurt your job.
To put it in a nutshell, be smart about your actions at work. We are in an unstable economy and our jobs are imperative for survival. Also for younger people each job you are with will be attached to your name forever. Keep your work resume clean and attractive to look at.