'How do I make Varun greet visitors without having to prompt him each time?'

'How to make Preeti understand that she should not lie even if she gets less marks?'

These statements convey a pertinent concern of parents', i.e. of how to establish the desired behaviour and attitude in children.

The first step involved in achieving this goal is to be consistent in the expectations from the children. To appreciate this step, let us take the example of the confused 6 yr old Vinay.
 

Children get confused with contradictions, which parents often give for their own convenience

Vinay always gets a lecture from his mother on how 'action' movies spoil children. However the same movie becomes 'okay' when Shikha Aunty visits. At that time, his mother says, -'Vinay, go watch your movie while Aunty is here'.

 Maybe as adults, we can understand that Vinay's mother wants undisturbed time with her friend, so she lets Vinay be occupied in something he likes at that time. This arrangement is convenient for her. But for young Vinay, it is a matter of sheer confusion-'action' movies- allowed or not?

Just like Vinay's mother, many a times, parents tend to give contradictory messages about the same behaviour. According to parent's own convenience, at a particular time the same behaviour is allowed while at another time it is wrong. This inconsistency really confuses the child about what is exactly expected from him. If the child is not sure of what to follow, how can adults expect him to execute it?  This issue can be sorted out to an extent by paying more attention to how consistent we are in our messages about the behaviour we expect. In the example above, it would have helped better if it was genuinely explained to him that 'mummy' needed to spend time with her friends and some alternate healthy activity was suggested to Vinay. This would ensure consistency about not watching 'action' movie.
 

Children also get confused when parents are inconsistent in action and preaching

Another common way of parents being inconsistent is through their preaching a certain thing and actually doing else in reality. Kirti's father scolded her for hiding her classmate's homework. She was told that it was wrong to come up in the teacher's eyes by trying to bring someone else down. However she had seen her father invite his boss for dinner and talk badly of his colleague just before the promotion interview. As is obvious, by hiding the classmate's work, she also did what her father tried doing with the colleague. However she was scolded for the same, naturally, she does not know what to follow- the example of the father or his preaching. Again, here, inconsistency in the expectations about an attitude has really puzzled the child about what is actually to be considered right. 

I would just like to bring up here that there are times when adults consciously take steps that seem different from their own 'preaching' given to the child. For e.g.- at times parents do not take calls and get it conveyed to the caller that they are not present. Literally speaking, the child may feel that the parent is lying, which he has been told is wrong. At such times, the parent has to take care to explain to the child why such a seemingly contradictory step was taken. However in situations like these, the parents have to be clear in their conscience that they are not going against the values they advise and are using discretion in the particular situation.
 

Desired behaviour can be strengthened by paying attention to positive behaviour 

After the child is clear in what is expected from him, comes the next step in actually strengthening the desired attitude to make it a steady pattern in the child. Reinforcing the desired behaviour when the correct activity occurs can do this. Usually the method used to make children understand is to correct them when the child does something wrong. Like Varun is definitely reminded whenever he does not do his homework, but not given attention on the days he does his work. Instead if attention were given to him each time he does his work with encouraging statements like-  'I am so happy to see you doing your work ', it would establish the pattern of doing the homework in him. The process at work here is that the activity that gets more attention gets strengthened better. Even if with negativity, but if Varun gets attention each time when his work is not complete, this holds more value for him than the times when he gets no attention when he does his work. But once a child starts getting attention for the correct behaviour there would be no need for him to seek that kind of attention by doing the incorrect things. 

If these factors of being consistent in the expectations from the child and giving more value to the time when the desired pattern occurs are taken care of, it would become much easier to establish required patterns in the child.