My first mental prayers, being raised in a Protestant house, were prayers for salvation and forgiveness of sin, from about 6 forward.
"Oh God, save me. Oh God, I give you my heart. Oh God, help me to never lose you. Oh God, will I be saved?"
I remember always hearing the bell of the catholic Church toll and thinking to myself, "I will go to the Catholic Church one day." I remember looking at artwork of the Madonna and Child and thinking that Mary was beautiful, I remember visiting the California missions and thinking to myself, "How can these saints who love Jesus SO much all be SO wrong?" I was at least allowed a crucifix in my room from one of the missions. I also made vestments for myself and tried to "Say mass" when I was 10, which consisted of preaching of course.
It was all there growing up, coupled with a desire to be saved.
My second most common form of meditation would have been deliverance prayers. My mother is very spiritually proactive, and she taught us to go head to head with Satan when we felt oppressed, and to command him to be gone in the name of Jesus. So, right after, "Jesus save me" I learned, "I rebuke you Satan!"