Do not strain your neck or vocal cords. Project the sounds and do not force them. Understand and utilize the acoustical properties of the church building. In some churches, if you speak too quickly, meaning will be lost in the echoes. If you speak a little more slowly than you think you should, you're probably speaking at the best rate.
Concise articulation is essential.
Again, ask other lectors to critique you. Mean what you say. Create appropriate drama with body language, loudness, dynamic range, and inflection. But don't overdo it. Use only the drama that comes from meaning.