One is the assumption that praying = adoration, therefore praying to a saint (one in heaven, that is) amounts to polytheism or idolatry of some sort.
This is not the case, because an absolutely essential distinction must be made between Dulia, Hyperdulia,and Latria: between secondary, derivative and dependent forms of honor, and that supreme honor which is due to God alone.
Please do not take offense but this is what we believe.
Here are two key points (both from my wife, the “Biblical Scholar”):
1. As instructed by Jesus... we should pray this way...
“The Lord's Prayer
Our Father who art in heaven, hallowed be thy name. Thy kingdom come. Thy will be done on earth as it is in heaven. Give us this day our daily bread, and forgive us our trespasses, as we forgive those who trespass against us, and lead us not into temptation, but deliver us from evil.
For thine is the kingdom, and the power, and the glory, for ever and ever.
Amen.”
Notice that this prayer is directly to God. Mary, or any of the deified Saints, etc. are not mentioned.
2. This is all that you need to know.
John 3:16
For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
All of the ritual and the church hierarchy are embellishments.
Also, there are people, groups, churches that attempt to set certain members above the rest. This is wrong. And the two key points are a foundation of the Christian faith. Nothing more. :)