Chatbots succeed when a clear understanding of user intent drives development of both the chatbot logic and the end-user interaction. As part of your scoping process, define the intentions of potential users. What goals will they express in their input? For example, will users want to buy an airline ticket, figure out whether a medical procedure is covered by their insurance plan or determine whether they need to bring their computer in for repair? 

[In] artificial intelligence ... machines are made to behave in wondrous ways, often sufficient to dazzle even the most experienced observer. But once a particular program is unmasked, once its inner workings are explained ... its magic crumbles away; it stands revealed as a mere collection of procedures ... The observer says to himself "I could have written that". With that thought he moves the program in question from the shelf marked "intelligent", to that reserved for curios ... The object of this paper is to cause just such a re-evaluation of the program about to be "explained". Few programs ever needed it more.
A chatbot (also known as a talkbots, chatterbot, Bot, IM bot, interactive agent, or Artificial Conversational Entity) is a computer program or an artificial intelligence which conducts a conversation via auditory or textual methods.[1] Such programs are often designed to convincingly simulate how a human would behave as a conversational partner, thereby passing the Turing test. Chatbots are typically used in dialog systems for various practical purposes including customer service or information acquisition. Some chatterbots use sophisticated natural language processing systems, but many simpler systems scan for keywords within the input, then pull a reply with the most matching keywords, or the most similar wording pattern, from a database.
In a bot, everything begins with the root dialog. The root dialog invokes the new order dialog. At that point, the new order dialog takes control of the conversation and remains in control until it either closes or invokes other dialogs, such as the product search dialog. If the new order dialog closes, control of the conversation is returned back to the root dialog.
Screenless conversations are expected to dominate even more as internet connectivity and social media is poised to expand. From the era of Eliza to Alice to today’s conversational bots, we have come a long way. Conversational bots are changing the way businesses and programs interact with us. They have simplified many aspects of device use and the daily grind, and made interactions between customers and businesses more efficient.
ELIZA's key method of operation (copied by chatbot designers ever since) involves the recognition of clue words or phrases in the input, and the output of corresponding pre-prepared or pre-programmed responses that can move the conversation forward in an apparently meaningful way (e.g. by responding to any input that contains the word 'MOTHER' with 'TELL ME MORE ABOUT YOUR FAMILY').[9] Thus an illusion of understanding is generated, even though the processing involved has been merely superficial. ELIZA showed that such an illusion is surprisingly easy to generate, because human judges are so ready to give the benefit of the doubt when conversational responses are capable of being interpreted as "intelligent".