I need some tips on how to give potty training of a 18 months old child?

18 months too early: 18 months may be too early to begin to potty train. At this age, the best you can do is to get a child interested in the concept of potty training. You can read books and purchase toys that highlight how to use the potty. The average age that children in the us are potty trainined is by three. What you don't want to do is create negative associations and feelings of stress around potty training.

A toddler who walks: from room to room, pulls his/her pants & pull-up or underpants up & down & says " pee-pee", "poo-poo" or "potty" to indicate he senses the urge to "go" is ready for daytime toilet training. If not, you may create a behavior problem . There's no harm in putting a potty chair in the bathroom for the child to sit on while you model using the toilet, but don't force the child to sit on it.