Warren Buffett, one of the world’s most successful investors and generous philanthropists, is often quoted as saying, “It takes 20 years to build a reputation and five minutes to ruin it. If you think about it, you’ll do things differently.”

And it’s worth thinking about. When it comes to your career, building a reputation is as important as building your resume. And it’s much harder to change.

How and where do you begin? And what should you keep in mind as you navigate the working world?

be on time

Construction happens. Traffic can be a beast. Things don’t always go as planned. We know this. So give yourself extra time to accommodate the things that should be exceptions but can turn into the rule.

According to one study, up to 20 percent of the U.S. population is chronically late, and not because they don’t value others’ time. These habits often trace back to childhood.

The solution? According to researcher Diana DeLonzor, author of Never Be Late Again: 7 Cures for the Punctually Challenged, be realistic about how much time your commute takes and give yourself some buffer time.

Set a routine so it becomes a habit and do everything you can to prepare the night before. Finally, get comfortable with downtime. If you’re early, look at it as a chance to catch up on emails, calls or just enjoy the quiet.

dress for the job

Dress codes exist for a reason. They remove doubt and distractions. No one wants to send someone home to change.

If you have questions on office culture, check with someone from HR or a recruiter. Still not sure what to wear? Err on the side of caution and keep it sensible, at least until you get a feel for the environment and your role.

give us your undivided attention

Does this sound impossible? We walk, talk and check texts on our phones. Surf the web and watch TV. But what does this say to those around us? We don’t think what’s in front of us deserves our full attention.

Put your phone in your desk drawer and check it on breaks and at lunch. And save social media for when you get home.

deliver on your promises

It’s tempting to say yes to everything, especially in the beginning when you want to make a positive first impression. But overpromising and under-delivering can be worse than saying no.

The key is to communicate and clarify expectations up front — and along the way. Check in at the start of a project and be clear about goals throughout.

Spend five minutes now considering the small things you can do to make a difference in how you’re perceived at work. Sometimes all it takes are a few tweaks to build a reputation you can be proud of.

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