Like most other solvers, I prefer to complete the grid through my own knowledge or ability, but it is good to share through this particular website. We don't just take answers, we give some too.
Over the years, I have won a number of prizes from the Catholic Herald crossword. The number of times I have been able to complete the grid without reference to a book, are few. Generally, though, I will try to work out what the answer is first, and then confirm it with a text book or concordance.