The details are what change from one company to another and from one fence from another. Questions you need to ask:
What kind of lumber am i getting for posts, structural boards, and fence boards?
Do you warranty it?
What kind of nails are you using?
Are you using those fence clips? Why?
How deep are you setting the posts? Is it always the same depth? Why?
So in what scenario will my estimate price change? Why?
I always find that by asking those questions you will find out what kind of fence each company is putting in. I usually try and mention what separates my company from others. Im never one to attack others and what they do. But i will mention that corners are cut and that can cost years when it comes to the lifespan of a fence.