I can't remember to hear "I hoped..." in any movie I've watched. I always hear "I was hoping..." when people talk. Nevertheless I know both forms are correct in terms of grammar. So when "I hoped" is more proper then "I was hoping" and vice versa?
In typical narratives about past events the past simple is the default tense. However, if the speaker wishes to convey the ongoing nature of the past action or state, then the past continuous can be used. For example:
In the days before the wedding I was hoping that the weather would be good.
You might also have encountered the past continuous more often because it is commonly used as a stock phrase to formulate a polite request.
I was hoping you could lend me some money
is more tentative than:
Can you lend me some money?
"I hoped" and "I was hoping" are almost interchangeable, however there is a slight tendency for "I hoped" to indicate a more fundamental and longer term desire than "I was hoping" which has a tendency to indicate something more immediate and transitory.
For example one would probably say "When I chose to study accountacy and business practice I hoped for a career in the financial sector" but go on to say "When I applied to PWC I was hoping to be taken on as a graduate trainee".
Another example would be "As a twenty-something I hoped to find a loving wife some day" as opposed to "As our wedding day approached I was hoping that the weather would be fine". The first is longer term, more fundamental and more abstract whereas the second is more shorter term, more concrete and more specific.
However these are slight differences in emphasis, not hard and fast rules.