Gauge the relationship. Before communicating or professing love for someone else, it is important to determine how the other person feels about you and how the relationship is going. If the relationship is fairly new, it might not be the best time to jump into "I love you's." People express their love for each other by how they treat the other person. A guy's actions will tell you more than words can. Does he demonstrate his love through his behavior? This is a good indication of how seriously the guy regards the relationship. Taking stock of how the relationship is going before saying anything will help determine if the time is right.
Think about timing. Just blurting out "I love you" in the middle of a conversation puts the other person on the spot and forces them to say something. The guy should not feel pressured to respond; you are looking for an honest exchange. Instead, wait for an opportune moment; perhaps a romantic evening together when you are intimate or having a positive and deep conversation about your relationship.
Use soft wording. Gently lead into the topic by talking about the positives of the relationship and some of the feelings associated with it. Keeping the conversation about your feelings makes him feel less pressured. For example, if the communication is more about how you discovered that you love this guy, it is framed as a self-realization (which it is) rather than as a feeling of attachment. Explaining the thought process first though a discussion of the relationship will help him better understand where you are coming from.
Remain calm and confident. The behavior and communication style of the person saying "I love you" will play heavily on the reaction. If the person is nervous and meanders by saying "I've got something to tell you" or "I'm not sure if I should tell you this," it makes the discussion more serious and adversarial. Instead, the conversation should flow smoothly and casually into the topic. If you are saying "I love you," say it like you mean it. There is nothing to be ashamed of or embarrassed about, and he should respect you for being open and honest.
Have no expectations. Do not say "I love you" simply because you want to hear it back. Say it because it is something that you have to tell the other person no matter what. Imagine that you said it and the guy did not say it back; would you still want to have said it? If you wouldn't, then perhaps you're not ready to utter those three little words.
Remember that when it comes to love there are no rules. Each relationship is unique and dynamic. Some couples can say they love each other within hours of meeting, and for others it may take years. No one knows you, your partner and the relationship better than you do. Use your best judgment and speak from the heart.