To begin with

Observe the child intently, but it is always better that the child doesn't know that he is being observed, as it might reflect upon his behavior.The best way this can be made possible is by not interfering when the child is doing something or by just allowing the child to work with someone he is comfortable with. I don't think there is any specific period for which a child has to be observed. The child can be observed till the required information is collected.

Never plan on how the observation should go on and try not to expect the child to exhibit behaviors that you are looking for . The policy i feel that helps us a lot is to just trying to gather as much as data from whatever the child is doing rather than collecting data according to what we want.It will surely be useful sooner or later.

once observation is done, then comes the next stage........