They called it “Showtime”—the decade from 1979 to 1989 when the Los Angeles Lakers dominated professional basketball by winning five championships. And in the midst of it Michael Cooper was named NBA Defensive Player of the Year.

Fast forward to 2010. After an illustrious career in the pros, Cooper is named the new head coach of the University of Southern California women’s basketball team. He delivers BIG, beating archrival UCLA 70–63. The former Showtime star strides confidently into the post-game press conference and offers up his pearls of wisdom on the game: “My opening statement is [expletive] UCLA.”

Uh-huh. Man knows how to make an impression. Too bad it’s not a good one.

Fortunately for Cooper, a contract and a big win under his belt afforded him the opportunity for a do-over. He released a public letter of apology to UCLA’s coach and players, and his blunder will soon fade from the headlines.

But what if you screw up when you don’t have a safety net?

These days a lot of people are temping, interning, and volunteering in hopes of finding permanent jobs. And any faux pas can cost them their chance for long-term employment. Beware of making these potentially fatal mistakes:

• Tardiness. Whatever it takes, arrive on time. When you show up late—even for a volunteer position or internship—you signal your supervisors that you’re unreliable. If you can’t be trusted to take small responsibilities seriously, why should they trust you with a paid or permanent position? And don’t clock-watch, either. You don’t want to give the impression that you can’t wait to drop everything and leave when your shift ends.

• Whining. Do. Not. Complain. It doesn’t matter if everyone around you spends the day moaning. Don’t join the whine-fest. If the boss starts to wonder about the source of all the negativity, your fellow town criers won’t hesitate to throw the temp/intern/volunteer under the bus rather than put their own necks on the line. They’ll figure you have nothing to lose. Do you want the job or not? If not, find another place to temp. But if you genuinely want to work for the organization, then focus your attention on the positives instead of the negatives. Employers are more likely to make a permanent place for those who brighten the environment than those who make it even more miserable.

• Disinterest. Demonstrate your interest in long-term employment by asking questions about the job and the organization. Ask how you can improve your skills/performance to become more of an asset to the company. Volunteer to pitch in with tasks no one else wants to tackle. The more engaged and helpful you appear, the more likely you are to make a good impression—and find a permanent home.