Check your My Page.
I found sending questionaires, comic strips, and pictures were the best. As my son told me after, his RDC told him, "have them send cookies. I LOVE getting cookies!".....in other words, don't expect them to reach your recruit.
Oh, and musical cards are especially fun for the RDC's.....so....depends on how much you love your sailor recruit.
Oh, and then there's glitter. The RDCs will show ALL the recruits just how much they adore glitter.