Lead qualification is the process of determining how close your prospect is to making a buying decision. The best way to find out is to ask your prospect directly, through calls or face-to-face visits.
To get the answers you are looking for, you must ask the right questions, so consider the following aspects:
Customer profile: Does your prospect's profile match your qualified prospect? What similarities do you have? What industry does he/she belong to? What content from your website or blog is he/she consuming?
Needs: What needs does he have, is he aware of his needs, what is his emotional pain, what is he looking for, does your product or service match what he is looking for?
Decision making process: What stage of the buying process is your prospect in? Are other people involved in the buying decision? Is your prospect a decision maker?
Competition: What advantages does your product have over the competition? Why would the prospect decide to buy from you and not from the competition?