Observe Other People While They Talk
Very basic thing writer must have is to observe other things what are going on around him.This habit of observing other people can help in designing your characters, dialogues and for your plots. So, try to observe the other people while they talk for writing realistic and natural dialog. Listening to this type of conversations need lot of patience and smart thinking because when time arrives u should be in state to recall the conversations and use them in your script with few changes. Don't do this like a work, make it an habit to listen to others.Should Be Realistic And Natural But Not 100%
Always remember, writing a dialog for a movie is a challenging job,why because you should give your audience everything that sounds natural but at the same time it should not be too natural. Like what you talk or behave. But it should give an impression that your character is behaving in a natural way. So, to avoid this always filter unnecessary and unwanted words from your dialog which doesn't add any meaning to your characters needs or which doesn't help to add to your main plot. By doing so your are writing a dialog which is to the point and natural.Don't Get Into Head To Head Conversations
Yes this is the most important thing you have to keep in mind when writing a dialog. In the process of writing without any notice u can get into head to head conversations with your characters. This head to head conversations will come out as a discussion between your characters which can create boredom to your viewer. so, avoid head to head conversations as much as possible.Don't Add All the Information In Your Dialogues
Yes, never use your dialog as a information carrier. Always write a dialog to the point and only provide necessary information that is need for a particular scene or script. Viewer can relate and remember the information what you have provided earlier so don't panic and unfold your twists in your story naturally.Use Descriptions In Between
Always try to use insert some sought of descriptions when ever necessary when writing a dialog.This will break your dialog and action into two parts and helps to tell your story in a more compact manner. This is a very useful way of writing a dialog which helps to filter your action and description in two different ways.Follow Proper Grammar Rules And Punctuation
Always remember, punctuate your dialog in a correct way. A full stop and a comma can change the rhythm of your script. Punctuation have lot of importance when your write your dialog. So, be careful about your grammar and punctuations.Use Dialogue Tags That Don't Distract
Always remember, whatever you do while writing a script or a screenplay your target must be your audience. Never make them distracted. Use very simple dialog tags such as she said/he said rather than she replied it arogantly etc., This might sound good but it will distracts the viewer on to the other things. So, be very careful.Use Slang's And Dialects In A Appropriate Way
Yes, especially in Andhra Pradesh we have many number of slang's and dialects,So use them in a minimum way so that it should n't bore your viewer. It can be good for designing your character but don't do it in a heavy dosage. It may damage your characters bond with the audience.Always Revise Twice or Thrice While You Write
Yes always try to read and analyze your dialog when as many times as possible. Don't ever get compromised with the output quality. Reading again and again brings loads of clarity like where you have gone wrong. what's your character talking, etc., by looking into these minute things you can write more effective dialog.All these are the small rules to write a effective dialog. Try to follow these and add if you know few more in comments section below.Try to give your feedback.