How do you feel a girls boob?

Begin with the boob feeling by asking the girl if you can do it. If she says yes, then start feeling. I would suggest beginning the feel-up by rubbing her breasts over her shirt while you kiss her. Don't just stare at her breasts. Keep her occupied with kisses. With your hand, make a small circular motion over her breast. Take it in your hand like you would an Apple. Squeeze a little here and there, very gently. If she's flat chested, just rub the surface of her chest with the palm of your hand. Use your finger tips to see if you can feel her nipples through her shirt. Rub down the side of her body, too, and up her neck to her hair. Keep kissing her.

Then put your hand up her shirt and do the same.