There is someone in your group (or group of friends) who needs a confrontation. They've done something to harm you, themselves of your group. You've decided that you're going to "have the talk," and you're starting to figure out the when and how.
It's important that you reduce the drama. A few tips:
Stop the electronic communication. Fiery emails, or six-page messages that pour out gobs of emotion are just going to make things worse. Move everything to the realm of face-to-face. Sometimes your "radio silence" will let people know that you're serious about dealing with the situation. Encourage others to cease the messages also. More drama is not what you need at this critical time.
Isolate the behavior. Write down the facts. What happened? Narrow the scope of your confrontation to the behaviors that were harmful. You're unlikely to change someone's style or personality, so don't try. Target the one specific thing that happened.
Talk to another friend about it. Look for that person you trust who will help you process the situation. Are you over-reacting? Are there other incidents you haven't heard about? Vocalizing your feelings and motivations for a confrontation to a caring friend FIRST can really help build your confidence. You might even do a role play, having the other person pretend to be the person you plan to confront.
Check your level of anger. Are you having trouble sleeping because your mind is racing? Are you distracted and pissed off about the situation? If so, you might be the wrong person to do the confrontation, and you might need to consider approaching another friend or member to do the confrontation. Anger and unchecked emotion will not help you achieve your goals.
Let things settle down. I'm a big fan of letting a day or two pass to let things calm down. It's amazing how a day or two of perspective can affect the situation's intensity. If fear and emotion are detriments, give them a day or two to evaporate a bit.
It is important to confront negative behavior, but there is no rule that says you have to do it within 24 hours. Confrontation mixed with drama almost never leads to change. Calming the situation down before constructively confronting someone is almost always the best way to go.