Good friends give us emotional support, professional leads and add dimension — and excitement — to our lives. But many people wind up with friends who drain, discourage and even betray them.

These toxic friends aren't always easy to identify. Too many people wait too long to take protective action. Our desire for personal relationships sometimes causes us to overlook offensive, hurtful behavior and to suffer unnecessary abuse.

TOXIC TYPES

It's hard to admit to ourselves that a friendship isn't working out. But holding on to a toxic friend can demoralize you and even keep you from reaching your potential in other areas of your life.

The most common types of toxic friends...

1. The stifler. Your opinion doesn't matter much. If your point of view doesn't match his/hers, he/she gets upset. This person can't tolerate difference and won't let you be yourself.
2. The sniper. Whether he's hostile or just insensitive, this type keeps finding ways to put you and your decisions down.
3. The drainer. This type asks for your help — but when you need a favor, he is too busy.
4. The dropper. He is always on the lookout for a better opportunity. If someone with more power, money or connections comes along, this friend suddenly starts spending less time with you.
5. The big mouth. This person can't resist passing along sensitive information that you shared in confidence.

True friends, on the other hand, consistently affirm and support you. You may not always agree, but you know that you have each other's best interests at heart.

PRUNING YOUR FRIENDSHIPS

To determine whether your friends are true friends, assess your personal relationships at least once a year. Questions to ask yourself...

• Am I mostly satisfied with this particular relationship?
• Do I feel bad about myself after spending time with this person?
• Do I have to censor myself?
• Am I doing most of the giving?
• Can I turn to this friend in a crisis?
• Does this person take pleasure in my victories... or do I have to soft-pedal my successes?

If you're dissatisfied, try to figure out what is wrong. There may be steps you can take to save the friendship -- sometimes it's as simple as airing a grievance.

You may also be able to scale back the friendship without ending it. Some friendships work fine as long as you're able to keep the appropriate distance.

Example I: A self-centered friend may be an entertaining guest at parties -- but not someone to whom you can confide your feelings.

Example II: An unpredictable friend may be fun to go out with for a drink on a Friday night -- but the wrong person to count on when you need a lift to the airport.

The most diplomatic way to reduce contact is to tell a toxic friend that you're swamped with work -- until he stops calling. If the message doesn't get through, be more direct -- but still be gracious.

Example: "My life has changed, and I'm just not socializing as much as I used to."

BUILDING TRUE FRIENDSHIPS

Besides protecting yourself from being hurt or manipulated, another reason to be aware of toxic friendships and deal with them is to be able to give your true friends the energy and time they deserve. To help your most valuable friendships flourish...

• Make time together a priority. Don't shortchange your true friends. If scheduling is a problem, combine visits with other activities.

Examples: Go to the movies or the gym together. Meet at your kids' soccer practice. Have coffee together before you do your weekend grocery shopping -- many supermarkets now have sit-down delis or cafés that make this easier.

E-mail is another good way to keep in touch. Sharing the little details of daily life helps to cement a friendship -- and you can do this electronically without worrying about waking your friend in the middle of the night.

• Take the long view. Though there should be an exchange of support, you need to be understanding when a friend is temporarily unavailable -- physically or emotionally -- for good reason.

Offer your support if needed... and be as patient as you would want your friend to be with you.

• Don't let annoyances build up. If something is bothering you, say so early. It's easy to misinterpret others' intentions and blow a situation out of proportion. Give each other a chance to clear things up.

Helpful: When expressing yourself, use the I approach -- I felt hurt, I was disappointed -- rather than you did... or you are... attacks.

• Be willing to apologize. It's human to let each other down once in a while. A sincere apology can bring friends closer together.

Reminder: A true apology begins, "I'm sorry I... ", not "I'm sorry you... ."

• Celebrate each other's successes. A true friend is genuinely excited when something good happens in the other person's life.

If you feel envious of a friend who experiences good fortune, don't let it compromise the relationship.

Instead, turn envy to good use. Ask yourself, What would I need to do to have what I want? Then ask for your friend's insights on how to get there.

Florence Isaacs, has been writing about relationships for more than 20 years, New York. She is author of Toxic Friends, True Friends: How Your Friends Can Make or Break Your Health, Happiness, Family, and Career (Morrow).