Simply, you viral model must be scalable. If it is successful, you must be prepared to accommodate you new customers. Offers something directly relevant to consumers Your marketing strategy must get into the heads of people. You need to figure out their behaviors and motivators. If you do that and implement it into the model, you will be successful.
Viral marketing capitalizes on people's network.
You want to get in-between those transactions that already occur. If a friend's email is attached with message, they are giving it credibility, thus the person is more likely to trust the product or service and try it. Distribute your information in a way that uses other people's resources. Websites, newsletters and affiliate programs are a good example of this. By getting organizations to host your message, you are using their resources instead of your own.