1. Are you prepared? You have to give them a real reason - not just an emotional one. However, you have to realize that many of their reasons for being a Christian are emotional, so be ready to show atheism in an emotionally positive light.
2. Think about your friendship. Are the two of you close? If not, try to increase your friendship before attempting to change their religious beliefs. However, do not do this merely because you are trying to score points, or because their beliefs offend you. Similarly, if you aren't certain of your own beliefs, you may be using them to justify your own, purely emotional, decision. You must have a genuine interest in being your friend's well-being and want to help them give up superstition.
3. Educate yourself. The key to converting someone is to understand their position. Read everything you can about atheism, Christian apologetics and religious history. Most Christians don't know how their religion came to be, so it is useful to be prepared in this area. Learn their common arguments and the best rebuttals. Also, examine myths, urban legends, and superstitions and learn why people tend to believe such things. It will help to know something about the psychology of belief, including the process of indoctrination. Read and understand their holy book cover to cover. Study subjects in physics and biology, Christians often use flawed arguments and this way you can counter them.
4. Start off casual. You should first show how atheism has impacted your own life in a positive way. Citing peer-reviewed scientific publications at every possible opportunity may be a bit much. However, if they bring up that God did this or that in their life, it is ok to point out to them other factors that helped them, such as probability, their own work, or a professional's skill. It may also be useful to point out atheist role models.
5. Get them in the habit of questioning their own faith. Sometimes pointing out a single fallacy every now and then is good, or asking them to explain something about their religion you didn't understand (ie If Hitler repented, would he go to heaven?)
6. Let them try to convert you. Many Christians will automatically try to convert you. This is the easiest way to engage them, especially if you are familiar with the arguments they use. Just by being calm, firm, and reasonable, you are already frustrating everything they've been told about "immoral, angry atheists". Of course, don't get trapped at a conversion party, and be especially aware of genuinely dangerous cults.
7. Give your friend practical advice for their problems from respected books from respected experts in the field. If your friend tells some wisdom from the Bible, point out how you can come to that wisdom outside of religion. Show how you come to your views from practical roots.
8. Socialize them. Help them mix outside their own narrow circle of believers, to see other viewpoints. They may have never considered other views but those handed down by their church and peers. Make sure any atheist friends know not to attack them, or obsess over religious differences. Atheists don't spend much of our lives worrying about "being better atheists", we just don't do religion; get your Christian friend used to living without religion.
9. Don't change them. Don't try to change them too drastically. Deconversion is a highly personal activity that inherently takes a long time. Changes are gradual, so don't push too hard. Let the person come to their own understanding of a world without any gods.
10. Know when to ease up. Some people just truly don't want to accept that god is fictional. If this is the case with your friend, and you've tried everything else here, don't push any further. There is nothing more that you can do. Don't let it be cause to end your friendship, but know when to leave them be.
11. Be open-minded. Listen and understand their point of view. Learn what makes them believe what they do. Remember, we can't prove, in any absolute sense, that no gods exist. We can only show evidence that gods and religion have truly human origins, point out inconsistencies in their belief, and show how scientists and philosophers have answered many of the grand questions of life. We can only show that the world doesn't end when your faith does.
At another forum where they were coming from to join here. They had a complaint about the thread on no morals for atheists. Well the example above is done off pure deception. Ti sun it up, the atheist cannot be like he is. He has to act nice, he has to act like he cares, he has to act like he is interested, and he has to get his Christian buddy to question his own belief. Basically a covert full blown deception in order to get them to convert (evangelize).
I'd basically say that would be the definition of no morals, especially since they would not have any problem doing that to a friend.
This my brethren, is the perfect example of the anti-Christ spirit live and well. This is because this is what it's going to take for the anti-Christ to gain control is for the masses to think just like he does. The sad situation to the whole thing is that the atheists have no clue.
They are, by their own actions, fulfilling prophecy. Because who else who stand behind the anti-Christ except militant atheists?