There are few mistakes you can make at work that will cost you your job.
Most of the things people are afraid of doing -- like failing on a major project -- generally still end in a promotion or another major project if your boss can see you worked hard. The real reputation killers are things you wouldn't expect to be a big deal, but they are all things your boss is more likely to notice than how hard you work.
Here are the traps to avoid:
Arriving late to work
Once or twice is excusable. Everyone is late occasionally when a bus breaks down or there is an emergency at home. But if you are late habitually -- more than once a month -- you are doing something wrong. If your route to work is unreliable because traffic is bad or the train tracks sometimes flood, leave earlier to get to work, even if this means often being half an hour early. That's what habitually on-time people do. When people arrive and leave is one of the few things a boss can always look up, even if he doesn't see you coming in late each day. Avoid drawing negative attention to yourself by being on-time.
Submitting your time sheet late
This is one that doesn't seem like it should be such a big deal, but it is. The reason is that your boss most likely receives either an automatic electronic alert or an actual person yelling at him every time your time sheet is due and you haven't submitted it yet. Whether you are a temp, consultant, full-time hourly, or salaried employee, this is most likely the case. Even if you never do anything else wrong at work, regularly submitting your time sheet late will ensure that your boss hears your name for a negative reason at least once a week. Avoid this reputation killer by setting your own reminders each week on your own computer or calendar.
Dressing inappropriately
Wearing jeans when the official dress code says not to may seem like a victimless crime, but you're actually hurting yourself. Even if no one mentions your dress code violations, everyone at work can see them. Your boss and other higher-ups will interpret your inability to follow the dress code as either inability to follow directions or willful disobedience. Either way, it makes you look unprofessional and unpromotable to everyone around you.
Getting into fights with colleagues or clients
One of the worst things you can do on the job is get into shouting matches. They make you look like you can't control yourself, and that can scare your boss and others into firing you altogether. The best way to win any fight that arises on the job is to keep the argument verbal -- meaning nothing physical and nothing written down for future reference either -- and to refuse to raise your voice. If someone screams and swears at you, responding in a cool fashion at a normal volume makes you look like the sane one who is obviously in the right. Then avoid contact as much as possible with that person in the future -- if he even manages to keep his job.
There are very few mistakes you can make on the job that will cost you your good reputation. However, the little careless things that don't seem like they should matter can really add up. Avoid these reputation killers and your boss will have to focus on other things -- like how well you do your actual job.
Carissa Doshi is a business writer and the president of Gen Y Media Group. She gives career advice and blogs about her experiences on www.carissadoshi.com. You can also follow @CarissaDoshi on Twitter.