In the LDS faith the youngest age that someone can qualify for baptism is eight. In fact, LDS members are commanded to baptize their children by this age or the child’s sins will be on their head (D&C 68:25). The reason given is that is the age (in LDS theology), which a child can distinguish right from wrong (i.e. they can sin).
I was baptized at the age of eight. While I barely remember the event, I do know it was not defining moment in my life. That came much later when I obtained a testimony for myself. Baptism was something I did because it was expected and because the anticipation was something like waiting for your birthday to arrive. I sometimes wish that I could have waited until later in life, when I had gained a testimony of Christ as my Savior. I think it would have meant much more to me then.
That said I have to admit that the age is arbitrary because different people will come to this understanding at different ages. Maybe someone who’s eight can have a deep appreciation for Christ. Surely this is a better approach than some religions that baptize infants who have no idea what is going on, but perhaps others who require that the convert be conversant in their doctrine and active for some time, would be the best. I think there are pluses and minuses to all these approaches. The Bible gives little enlightenment on the subject of age when it comes to baptism. If we believe that the Savior was the supreme example to be followed I suppose we should at least acknowledge that persons being baptized should at least be aware of what they are doing and why. What do you think?