Each person develops their own personality and character as they go through life, this is what makes the person so special and unique. A lot of people choose to read passages from the Bible rather than a poem because they think that this is more appropriate.
The most common and sincere way of extending your sympathy is to say I am sorry to the bereaved for his loss. The details that a funeral home will take care of include the care of the body, the hosting of a wake or viewing, the funeral services either there or in a place of worship and the burial. Included in the details of these funeral burial services are a number of choices including a person to lead the service, flowers, music, and even photos if you choose to honor the deceased in this way.
Remember to be sincere, as it will be felt by the congregation. If you were best friends since high school or college, then talk about the good times you had and how he helped you during those years. Humor in good taste relieves stress and anxiety, and it's almost certain to be welcomed by the funeral guests.
As hard as it may seem right now, it gets better. If you are gifted with the blessing and talent of writing poetry for the dead, share it.