Q:

What are the restrictions on United when applying credit from a cancelled flight?

If I cancel a United flight, from what I understand I'll get credit toward a future flight, but I'll have to pay a fee of $300. But what I can't seem to find out is

Does the future flight have to be the same departure/arrival airports?
Does this credit expire (e.g., after  a year?)
Can I apply credit toward any future flight (perhaps with the restriction in the first bullet), or do they restrict to a small subset of future flights?

Maybe there's a page somewhere that explains all this, but I can't find it after searching both the United website and Google.

A:

Part of the reason it's hard to find general information is that different tickets may have different change/refund policies and fees, depending on the type of ticket you buy, booking class, and other factors.  So to be sure of having the right answer, you have to read the fine print in your ticket, or call the airline if necessary.
However, my experience is that the following policies are typical for non-refundable tickets on United and the other major US airlines:

Whether you change or cancel the flight, the effect is pretty much the same: they take the original price of your ticket, subtract the change fee (if any), and let you use what's left as credit toward any new flight(s) on their airline.  There are normally no restrictions as to where you can fly; the origin and destination can be completely different from the original flight.  If the new flight costs more than your credit, you have to pay the difference.  If it costs less, you can use the difference on another flight.
The credit normally does expire.  In fact, a common rule is something like "all travel must be completed within one year of the original booking date".  So if you bought a ticket in March 2015 for travel in June 2015, and you want to change/cancel it, the new flight has to be not only booked, but actually flown, by March 2016.  (So it's not allowed to use that credit in February 2016 to book a flight for April 2016.)
There may also be a "no name changes" requirement: it may be that you can only use the credit to buy tickets for yourself (or whoever was originally travelling), not for other people.

