When to baptize?

What are your thoughts on when someone should be baptized? I was raised Catholic and am now Episcopalian, so I am familiar with infant baptism. Infants are baptized to welcome them into the church family. The congregation and Godparents make a promise to help raise the child to know Jesus until such time as they take on the job themselves. In the Catholic church, that is at Confirmation. My Episcopal church goes through Rite 13 and Confirmation. My next door neighbor goes to a church that baptizes adults because she says they wait until the individual gives their own consent because it is a big deal. Both of those reasons make sense to me. I am curious about this because the same neighbor just went to a baptism party for an 8 year old girl in her church. How is an 8 year old girl qualified to make that decision? Aside from saying "Jesus is good", which my 4 yr old can do, how is a child able to make such a big decision? Wouldn't 16 yrs or so would be better? More adult?