The first time you say "no" to your baby.
When your baby starts to crawl and explore his/her surrounding, saying" no" to baby comes naturally when he/she starts getting into mischief. I learned this when my daughter turned 8 months old and started getting good at getting into everything. Setting limits is a good time around this age and making your home baby proof. I made my daughter a play area where I can keep an eye on her and I am in the process of Investing in an outdoor/indoor superyard, or as my husband would say the "Rug Rats corral" When was the first time you said no to your baby?