To sign pocket, take your dominant hand and form it into the ASL letter 'B' (thumb tucked in, four fingers stretched out and stuck together), but hold it upside down, palm facing you. Then make the motion of tucking that hand into an imaginary pocket in your pants, in your shirt, or wherever you want to show your baby that you actually have a pocket.
Teach this sign to your baby in the context of getting dressed and stuffing little odds and ends into the pocket of your clothes or other organizers at home.
Don’t be surprised if your baby develops a mild fascination with pockets. Teach your baby about pockets by giving him little trinkets to store in their pockets.