the start

就我的记忆来说……
As far as I can remember,...
What's John's last name? (约翰姓什么来着?)
As far as I can remember, it begins with M. (就我的记忆来说，它的第一个字母是M。)
To the best of my memory,...
As far as I know,... (就我所知……)
If my memory serves me right,... (如果我没记错的话，……)

以牙还牙，针锋相对。
Tit for tat.
John kicked me, so I gave him tit for tat.(约翰踢我，所以我以牙还牙。)