Take the time to discuss your son's strengths and weaknesses with him. Use yourself as a model by talking with him about some of your best abilities as well as some areas that you find difficult. Talk as well about the many types of talents in the world, and help him to recognize others who may be very similar to him or very different from him but also talented.
Once you have identified his strengths and interests, the two of you may want to choose an activity or two that builds on his abilities. If he's an advanced reader, there may be a children's reading group at the local library. If he shows talents in math or science, check into whether a local museum or science center offers classes for young gifted children. If he's a budding actor, community theater productions of musicals such as "The King and I," "Oliver!," or "The Sound of Music" may include children's parts. Focus on activities that he thinks are fun and that can also provide enrichment beyond his classroom experience.
Working with his school librarian or the children's librarian at a local public library, you can identify biographies of gifted persons to read with your son. Knowing that there are others like you can be reassuring and motivating.
A new book you might enjoy reading is Smart Boys: Talent, Masculinity, and the Search for Meaning by Barbara Kerr and Sanford Cohn. The book focuses on the specific challenges of gifted males and how we can nurture their development into bright, productive adults.